Add imip processing

Signed-off-by: Anna Larch <anna@nextcloud.com>

18 files changed, 1425 insertions, 10 deletions

diff --git a/appinfo/info.xml b/appinfo/info.xml
index 6becb7c3e..96e009bac 100644
--- a/appinfo/info.xml
+++ b/appinfo/info.xml
@@ -35,6 +35,7 @@
 	<background-jobs>
 		<job>OCA\Mail\BackgroundJob\CleanupJob</job>
 		<job>OCA\Mail\BackgroundJob\OutboxWorkerJob</job>
+		<job>OCA\Mail\BackgroundJob\IMipMessageJob</job>
 	</background-jobs>
 	<repair-steps>
 		<post-migration>
diff --git a/lib/BackgroundJob/IMipMessageJob.php b/lib/BackgroundJob/IMipMessageJob.php
new file mode 100644
index 000000000..371645c91
--- /dev/null
+++ b/lib/BackgroundJob/IMipMessageJob.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2022 Anna Larch <anna.larch@gmx.net>
+ *
+ * @author 2022 Anna Larch <anna.larch@gmx.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\Mail\BackgroundJob;
+
+use OCA\Mail\Service\IMipService;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\TimedJob;
+
+class IMipMessageJob extends TimedJob {
+	private IMipService $iMipService;
+
+	public function __construct(ITimeFactory $time,
+								IMipService $iMipService) {
+		parent::__construct($time);
+
+		// Run once per hour
+		$this->setInterval(60 * 60);
+		$this->iMipService = $iMipService;
+	}
+
+	protected function run($argument): void {
+		$this->iMipService->process();
+	}
+}
diff --git a/lib/BackgroundJob/PreviewEnhancementProcessingJob.php b/lib/BackgroundJob/PreviewEnhancementProcessingJob.php
new file mode 100644
index 000000000..6aaecc1f1
--- /dev/null
+++ b/lib/BackgroundJob/PreviewEnhancementProcessingJob.php
@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Anna Larch <anna.larch@gmx.net>
+ *
+ * @author Anna Larch <anna.larch@gmx.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Mail\BackgroundJob;
+
+use OCA\Mail\Service\AccountService;
+use OCA\Mail\Service\PreprocessingService;
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\IJobList;
+use OCP\BackgroundJob\TimedJob;
+use OCP\IUserManager;
+use Psr\Log\LoggerInterface;
+use function sprintf;
+
+class PreviewEnhancementProcessingJob extends TimedJob {
+	private IUserManager $userManager;
+	private AccountService $accountService;
+	private LoggerInterface $logger;
+	private IJobList $jobList;
+	private PreprocessingService $preprocessingService;
+
+	public function __construct(ITimeFactory $time,
+								IUserManager $userManager,
+								AccountService $accountService,
+								PreprocessingService $preprocessingService,
+								LoggerInterface $logger,
+								IJobList $jobList) {
+		parent::__construct($time);
+
+		$this->userManager = $userManager;
+		$this->accountService = $accountService;
+		$this->logger = $logger;
+		$this->jobList = $jobList;
+		$this->preprocessingService = $preprocessingService;
+
+		$this->setInterval(3600);
+		$this->setTimeSensitivity(self::TIME_SENSITIVE);
+	}
+
+	/**
+	 * @return void
+	 */
+	public function run($argument) {
+		$accountId = (int)$argument['accountId'];
+
+		try {
+			$account = $this->accountService->findById($accountId);
+		} catch (DoesNotExistException $e) {
+			$this->logger->debug('Could not find account <' . $accountId . '> removing from jobs');
+			$this->jobList->remove(self::class, $argument);
+			return;
+		}
+
+		$user = $this->userManager->get($account->getUserId());
+		if ($user === null || !$user->isEnabled()) {
+			$this->logger->debug(sprintf(
+				'Account %d of user %s could not be found or was disabled, skipping preprocessing of messages',
+				$account->getId(),
+				$account->getUserId()
+			));
+			return;
+		}
+
+		$dbAccount = $account->getMailAccount();
+		if (!is_null($dbAccount->getProvisioningId()) && $dbAccount->getInboundPassword() === null) {
+			$this->logger->info("Ignoring preprocessing job for provisioned account that has no password set yet");
+			return;
+		}
+
+		$limitTimestamp = $this->time->getTime() - (60 * 60 * 24 * 14); // Two weeks into the past
+		$this->preprocessingService->process($limitTimestamp, $account);
+	}
+}
diff --git a/lib/Db/MailboxMapper.php b/lib/Db/MailboxMapper.php
index 52e0b814c..d8c2ce895 100644
--- a/lib/Db/MailboxMapper.php
+++ b/lib/Db/MailboxMapper.php
@@ -35,6 +35,7 @@ use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\AppFramework\Db\MultipleObjectsReturnedException;
 use OCP\AppFramework\Db\QBMapper;
 use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\DB\Exception;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\DB\QueryBuilder\IQueryFunction;
 use OCP\IDBConnection;
@@ -129,6 +130,23 @@ class MailboxMapper extends QBMapper {
 	}
 
 	/**
+	 * @return Mailbox[]
+	 *
+	 * @throws Exception
+	 */
+	public function findByIds(array $ids): array {
+		$qb = $this->db->getQueryBuilder();
+
+		$select = $qb->select('*')
+			->from($this->getTableName())
+			->where(
+				$qb->expr()->in('id', $qb->createNamedParameter($ids, IQueryBuilder::PARAM_INT_ARRAY), IQueryBuilder::PARAM_INT_ARRAY)
+			);
+		return $this->findEntities($select);
+	}
+
+
+	/**
 	 * @param int $id
 	 * @param string $uid
 	 *
diff --git a/lib/Db/Message.php b/lib/Db/Message.php
index c01f7650b..d72ad5403 100644
--- a/lib/Db/Message.php
+++ b/lib/Db/Message.php
@@ -76,6 +76,12 @@ use function json_encode;
  * @method null|string getPreviewText()
  * @method void setUpdatedAt(int $time)
  * @method int getUpdatedAt()
+ * @method bool isImipMessage()
+ * @method void setImipMessage(bool $imipMessage)
+ * @method bool isImipProcessed()
+ * @method void setImipProcessed(bool $imipProcessed)
+ * @method bool isImipError()
+ * @method void setImipError(bool $imipError)
  */
 class Message extends Entity implements JsonSerializable {
 	private const MUTABLE_FLAGS = [
@@ -114,6 +120,9 @@ class Message extends Entity implements JsonSerializable {
 	protected $flagImportant = false;
 	protected $flagMdnsent;
 	protected $previewText;
+	protected $imipMessage = false;
+	protected $imipProcessed = false;
+	protected $imipError = false;
 
 	/** @var AddressList */
 	private $from;
@@ -152,6 +161,9 @@ class Message extends Entity implements JsonSerializable {
 		$this->addType('flagImportant', 'boolean');
 		$this->addType('flagMdnsent', 'boolean');
 		$this->addType('updatedAt', 'integer');
+		$this->addType('imipMessage', 'boolean');
+		$this->addType('imipProcessed', 'boolean');
+		$this->addType('imipError', 'boolean');
 	}
 
 	/**
@@ -316,6 +328,7 @@ class Message extends Entity implements JsonSerializable {
 			'inReplyTo' => $this->getInReplyTo(),
 			'references' => empty($this->getReferences()) ? null: json_decode($this->getReferences(), true),
 			'threadRootId' => $this->getThreadRootId(),
+			'imipMessage' => $this->isImipMessage(),
 			'previewText' => $this->getPreviewText(),
 		];
 	}
diff --git a/lib/Db/MessageMapper.php b/lib/Db/MessageMapper.php
index 6c6de1b20..5d62e9093 100644
--- a/lib/Db/MessageMapper.php
+++ b/lib/Db/MessageMapper.php
@@ -312,7 +312,6 @@ class MessageMapper extends QBMapper {
 				$qb1->setParameter('flag_notjunk', $message->getFlagNotjunk(), IQueryBuilder::PARAM_BOOL);
 				$qb1->setParameter('flag_important', $message->getFlagImportant(), IQueryBuilder::PARAM_BOOL);
 				$qb1->setParameter('flag_mdnsent', $message->getFlagMdnsent(), IQueryBuilder::PARAM_BOOL);
-
 				$qb1->execute();
 
 				$messageId = $qb1->getLastInsertId();
@@ -482,6 +481,7 @@ class MessageMapper extends QBMapper {
 				->set('preview_text', $query->createParameter('preview_text'))
 				->set('structure_analyzed', $query->createNamedParameter(true, IQueryBuilder::PARAM_BOOL))
 				->set('updated_at', $query->createNamedParameter($this->timeFactory->getTime(), IQueryBuilder::PARAM_INT))
+				->set('imip_message', $query->createParameter('imip_message'))
 				->where($query->expr()->andX(
 					$query->expr()->eq('uid', $query->createParameter('uid')),
 					$query->expr()->eq('mailbox_id', $query->createParameter('mailbox_id'))
@@ -505,6 +505,7 @@ class MessageMapper extends QBMapper {
 					$previewText,
 					$previewText === null ? IQueryBuilder::PARAM_NULL : IQueryBuilder::PARAM_STR
 				);
+				$query->setParameter('imip_message', $message->isImipMessage(), IQueryBuilder::PARAM_BOOL);
 
 				$query->execute();
 			}
@@ -520,6 +521,50 @@ class MessageMapper extends QBMapper {
 		return $messages;
 	}
 
+	/**
+	 * @param Message ...$messages
+	 *
+	 * @return Message[]
+	 */
+	public function updateImipData(Message ...$messages): array {
+		$this->db->beginTransaction();
+
+		try {
+			$query = $this->db->getQueryBuilder();
+			$query->update($this->getTableName())
+				->set('imip_message', $query->createParameter('imip_message'))
+				->set('imip_error', $query->createParameter('imip_error'))
+				->set('imip_processed', $query->createParameter('imip_processed'))
+				->where($query->expr()->andX(
+					$query->expr()->eq('uid', $query->createParameter('uid')),
+					$query->expr()->eq('mailbox_id', $query->createParameter('mailbox_id'))
+				));
+
+			foreach ($messages as $message) {
+				if (empty($message->getUpdatedFields())) {
+					// Micro optimization
+					continue;
+				}
+
+				$query->setParameter('uid', $message->getUid(), IQueryBuilder::PARAM_INT);
+				$query->setParameter('mailbox_id', $message->getMailboxId(), IQueryBuilder::PARAM_INT);
+				$query->setParameter('imip_message', $message->isImipMessage(), IQueryBuilder::PARAM_BOOL);
+				$query->setParameter('imip_error', $message->isImipError(), IQueryBuilder::PARAM_BOOL);
+				$query->setParameter('imip_processed', $message->isImipProcessed(), IQueryBuilder::PARAM_BOOL);
+				$query->execute();
+			}
+
+			$this->db->commit();
+		} catch (Throwable $e) {
+			// Make sure to always roll back, otherwise the outer code runs in a failed transaction
+			$this->db->rollBack();
+
+			throw $e;
+		}
+
+		return $messages;
+	}
+
 	public function resetPreviewDataFlag(): void {
 		$qb = $this->db->getQueryBuilder();
 		$update = $qb->update($this->getTableName())
@@ -1232,4 +1277,45 @@ class MessageMapper extends QBMapper {
 			);
 		return $update->execute();
 	}
+
+	/**
+	 * Get all iMIP messages from the last two weeks
+	 * that haven't been processed yet
+	 * @return Message[]
+	 */
+	public function findIMipMessagesAscending(): array {
+		$time = $this->timeFactory->getTime() - 60 * 60 * 24 * 14;
+		$qb = $this->db->getQueryBuilder();
+
+		$select = $qb->select('*')
+			->from($this->getTableName())
+			->where(
+				$qb->expr()->eq('imip_message', $qb->createNamedParameter(true, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
+				$qb->expr()->eq('imip_processed', $qb->createNamedParameter(false, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
+				$qb->expr()->eq('imip_error', $qb->createNamedParameter(false, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
+				$qb->expr()->eq('flag_junk', $qb->createNamedParameter(false, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
+				$qb->expr()->gt('sent_at', $qb->createNamedParameter($time, IQueryBuilder::PARAM_INT)),
+			)->orderBy('sent_at', 'ASC'); // make sure we don't process newer messages first
+
+		return $this->findEntities($select);
+	}
+
+	/**
+	 * @return Message[]
+	 *
+	 * @throws \OCP\DB\Exception
+	 */
+	public function getUnanalyzed(int $lastRun, array $mailboxIds): array {
+		$qb = $this->db->getQueryBuilder();
+
+		$select = $qb->select('*')
+			->from($this->getTableName())
+			->where(
+				$qb->expr()->lte('sent_at', $qb->createNamedParameter($lastRun. IQueryBuilder::PARAM_INT), IQueryBuilder::PARAM_INT),
+				$qb->expr()->eq('structure_analyzed', $qb->createNamedParameter(false, IQueryBuilder::PARAM_BOOL), IQueryBuilder::PARAM_BOOL),
+				$qb->expr()->in('mailbox_id', $qb->createNamedParameter($mailboxIds, IQueryBuilder::PARAM_INT_ARRAY), IQueryBuilder::PARAM_INT_ARRAY),
+			)->orderBy('sent_at', 'ASC');
+
+		return $this->findEntities($select);
+	}
 }
diff --git a/lib/IMAP/MessageMapper.php b/lib/IMAP/MessageMapper.php
index d70e6036d..b3a10bd57 100644
--- a/lib/IMAP/MessageMapper.php
+++ b/lib/IMAP/MessageMapper.php
@@ -665,6 +665,10 @@ class MessageMapper {
 										 array $uids): array {
 		$structureQuery = new Horde_Imap_Client_Fetch_Query();
 		$structureQuery->structure();
+		$structureQuery->headerText([
+			'cache' => true,
+			'peek' => true,
+		]);
 
 		$structures = $client->fetch($mailbox, $structureQuery, [
 			'ids' => new Horde_Imap_Client_Ids($uids),
@@ -673,19 +677,28 @@ class MessageMapper {
 		return array_map(function (Horde_Imap_Client_Data_Fetch $fetchData) use ($mailbox, $client) {
 			$hasAttachments = false;
 			$text = '';
+			$isImipMessage = false;
 
 			$structure = $fetchData->getStructure();
-			foreach ($structure as $part) {
-				if ($part instanceof Horde_Mime_Part && $part->isAttachment()) {
+			/** @var Horde_Mime_Part $part */
+			foreach ($structure->getParts() as $part) {
+				if ($part->isAttachment()) {
 					$hasAttachments = true;
-					break;
+				}
+				$bodyParts = $part->getParts();
+				/** @var Horde_Mime_Part $bodyPart */
+				foreach ($bodyParts as $bodyPart) {
+					$contentParameters = $bodyPart->getAllContentTypeParameters();
+					if ($bodyPart->getType() === 'text/calendar' && isset($contentParameters['method'])) {
+						$isImipMessage = true;
+					}
 				}
 			}
 
 			$textBodyId = $structure->findBody() ?? $structure->findBody('text');
 			$htmlBodyId = $structure->findBody('html');
 			if ($textBodyId === null && $htmlBodyId === null) {
-				return new MessageStructureData($hasAttachments, $text);
+				return new MessageStructureData($hasAttachments, $text, $isImipMessage);
 			}
 			if ($htmlBodyId !== null) {
 				$partsQuery = new Horde_Imap_Client_Fetch_Query();
@@ -720,7 +733,7 @@ class MessageMapper {
 				}
 				$structure->setContents($htmlBody);
 				$html = new Html2Text($structure->getContents());
-				return new MessageStructureData($hasAttachments, trim($html->getText()));
+				return new MessageStructureData($hasAttachments, trim($html->getText()), $isImipMessage);
 			}
 			$textBody = $part->getBodyPart($textBodyId);
 			if (!empty($textBody)) {
@@ -728,12 +741,12 @@ class MessageMapper {
 				if ($enc = $mimeHeaders->getValue('content-transfer-encoding')) {
 					$structure->setTransferEncoding($enc);
 					$structure->setContents($textBody);
-					return new MessageStructureData($hasAttachments, $structure->getContents());
+					return new MessageStructureData($hasAttachments, $structure->getContents(), $isImipMessage);
 				}
-				return new MessageStructureData($hasAttachments, $textBody);
+				return new MessageStructureData($hasAttachments, $textBody, $isImipMessage);
 			}
 
-			return new MessageStructureData($hasAttachments, $text);
+			return new MessageStructureData($hasAttachments, $text, $isImipMessage);
 		}, iterator_to_array($structures->getIterator()));
 	}
 }
diff --git a/lib/IMAP/MessageStructureData.php b/lib/IMAP/MessageStructureData.php
index 946649703..3c092a237 100644
--- a/lib/IMAP/MessageStructureData.php
+++ b/lib/IMAP/MessageStructureData.php
@@ -32,10 +32,15 @@ class MessageStructureData {
 	/** @var string */
 	private $previewText;
 
+	/** @var bool */
+	private $isImipMessage;
+
 	public function __construct(bool $hasAttachments,
-								string $previewText) {
+								string $previewText,
+								bool $isImipMessage) {
 		$this->hasAttachments = $hasAttachments;
 		$this->previewText = $previewText;
+		$this->isImipMessage = $isImipMessage;
 	}
 
 	public function hasAttachments(): bool {
@@ -45,4 +50,8 @@ class MessageStructureData {
 	public function getPreviewText(): string {
 		return $this->previewText;
 	}
+
+	public function isImipMessage(): bool {
+		return $this->isImipMessage;
+	}
 }
diff --git a/lib/IMAP/PreviewEnhancer.php b/lib/IMAP/PreviewEnhancer.php
index 23b0ddbef..a8c2cd531 100644
--- a/lib/IMAP/PreviewEnhancer.php
+++ b/lib/IMAP/PreviewEnhancer.php
@@ -109,6 +109,7 @@ class PreviewEnhancer {
 			$message->setFlagAttachments($structureData->hasAttachments());
 			$message->setPreviewText($structureData->getPreviewText());
 			$message->setStructureAnalyzed(true);
+			$message->setImipMessage($structureData->isImipMessage());
 
 			return $message;
 		}, $messages));
diff --git a/lib/Migration/FixBackgroundJobs.php b/lib/Migration/FixBackgroundJobs.php
index 121fe601d..403b8afe1 100644
--- a/lib/Migration/FixBackgroundJobs.php
+++ b/lib/Migration/FixBackgroundJobs.php
@@ -25,6 +25,7 @@ declare(strict_types=1);
 
 namespace OCA\Mail\Migration;
 
+use OCA\Mail\BackgroundJob\PreviewEnhancementProcessingJob;
 use OCA\Mail\BackgroundJob\SyncJob;
 use OCA\Mail\BackgroundJob\TrainImportanceClassifierJob;
 use OCA\Mail\Db\MailAccount;
@@ -59,6 +60,7 @@ class FixBackgroundJobs implements IRepairStep {
 		foreach ($accounts as $account) {
 			$this->jobList->add(SyncJob::class, ['accountId' => $account->getId()]);
 			$this->jobList->add(TrainImportanceClassifierJob::class, ['accountId' => $account->getId()]);
+			$this->jobList->add(PreviewEnhancementProcessingJob::class, ['accountId' => $account->getId()]);
 			$output->advance();
 		}
 		$output->finishProgress();
diff --git a/lib/Migration/Version2000Date20220908130842.php b/lib/Migration/Version2000Date20220908130842.php
new file mode 100644
index 000000000..133f2074b
--- /dev/null
+++ b/lib/Migration/Version2000Date20220908130842.php
@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2022 Anna Larch <anna.larch@gmx.net>
+ *
+ * @author Anna Larch <anna.larch@gmx.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Mail\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+class Version2000Date20220908130842 extends SimpleMigrationStep {
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		$messagesTable = $schema->getTable('mail_messages');
+		if (!$messagesTable->hasColumn('imip_message')) {
+			$messagesTable->addColumn('imip_message', 'boolean', [
+				'notnull' => false,
+				'default' => false,
+			]);
+		}
+		if (!$messagesTable->hasColumn('imip_processed')) {
+			$messagesTable->addColumn('imip_processed', 'boolean', [
+				'notnull' => false,
+				'default' => false,
+			]);
+		}
+		if (!$messagesTable->hasColumn('imip_error')) {
+			$messagesTable->addColumn('imip_error', 'boolean', [
+				'notnull' => false,
+				'default' => false,
+			]);
+		}
+		return $schema;
+	}
+}
diff --git a/lib/Model/IMAPMessage.php b/lib/Model/IMAPMessage.php
index 95ac594c8..c639bc8f1 100644
--- a/lib/Model/IMAPMessage.php
+++ b/lib/Model/IMAPMessage.php
@@ -733,6 +733,22 @@ class IMAPMessage implements IMessage, JsonSerializable {
 	}
 
 	/**
+	 * @return AddressList
+	 */
+	public function getReplyTo() {
+		return AddressList::fromHorde($this->getEnvelope()->reply_to);
+	}
+
+	/**
+	 * @param string $id
+	 *
+	 * @return void
+	 */
+	public function setReplyTo(string $id) {
+		throw new Exception('not implemented');
+	}
+
+	/**
 	 * Cast all values from an IMAP message into the correct DB format
 	 *
 	 * @param integer $mailboxId
@@ -779,6 +795,9 @@ class IMAPMessage implements IMessage, JsonSerializable {
 		$msg->setFlagImportant(in_array('$important', $flags, true) || in_array('$labelimportant', $flags, true) || in_array(Tag::LABEL_IMPORTANT, $flags, true));
 		$msg->setFlagAttachments(false);
 		$msg->setFlagMdnsent(in_array(Horde_Imap_Client::FLAG_MDNSENT, $flags, true));
+		if (!empty($this->scheduling)) {
+			$msg->setImipMessage(true);
+		}
 
 		$allowed = [
 			Horde_Imap_Client::FLAG_ANSWERED,
diff --git a/lib/Service/IMipService.php b/lib/Service/IMipService.php
new file mode 100644
index 000000000..100547513
--- /dev/null
+++ b/lib/Service/IMipService.php
@@ -0,0 +1,169 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Mail App
+ *
+ * @copyright 2022 Anna Larch <anna.larch@gmx.net>
+ *
+ * @author Anna Larch <anna.larch@gmx.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public
+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Mail\Service;
+
+use OCA\Mail\Account;
+use OCA\Mail\Db\Mailbox;
+use OCA\Mail\Db\MailboxMapper;
+use OCA\Mail\Db\Message;
+use OCA\Mail\Db\MessageMapper;
+use OCA\Mail\Exception\ServiceException;
+use OCA\Mail\Model\IMAPMessage;
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\Calendar\IManager;
+use Psr\Log\LoggerInterface;
+
+class IMipService {
+	private AccountService $accountService;
+	private IManager $calendarManager;
+	private LoggerInterface $logger;
+	private MailboxMapper $mailboxMapper;
+	private MailManager $mailManager;
+	private MessageMapper $messageMapper;
+
+	public function __construct(
+		AccountService $accountService,
+		IManager $manager,
+		LoggerInterface $logger,
+		MailboxMapper $mailboxMapper,
+		MailManager $mailManager,
+		MessageMapper $messageMapper
+	) {
+		$this->accountService = $accountService;
+		$this->calendarManager = $manager;
+		$this->logger = $logger;
+		$this->mailboxMapper = $mailboxMapper;
+		$this->mailManager = $mailManager;
+		$this->messageMapper = $messageMapper;
+	}
+
+	public function process(): void {
+		$messages = $this->messageMapper->findIMipMessagesAscending();
+		if (empty($messages)) {
+			$this->logger->info('No iMIP messages to process.');
+			return;
+		}
+
+		// Collect all mailboxes in memory
+		// possible perf improvement - make this one IN query
+		// and JOIN with accounts table
+		// although this might not make much of a difference
+		// since there are very few messages to process
+		$mailboxIds = array_unique(array_map(function (Message $message) {
+			return $message->getMailboxId();
+		}, $messages));
+
+		$mailboxes = array_map(function (int $mailboxId) {
+			try {
+				return $this->mailboxMapper->findById($mailboxId);
+			} catch (DoesNotExistException | ServiceException $e) {
+				return null;
+			}
+		}, $mailboxIds);
+
+		// Collect all accounts in memory
+		$accountIds = array_unique(array_map(function (Mailbox $mailbox) {
+			return $mailbox->getAccountId();
+		}, $mailboxes));
+
+		$accounts = array_combine($accountIds, array_map(function (int $accountId) {
+			try {
+				return $this->accountService->findById($accountId);
+			} catch (DoesNotExistException $e) {
+				return null;
+			}
+		}, $accountIds));
+
+		/** @var Mailbox $mailbox */
+		foreach ($mailboxes as $mailbox) {
+			/** @var Account $account */
+			$account = $accounts[$mailbox->getAccountId()];
+			$filteredMessages = array_filter($messages, function ($message) use ($mailbox) {
+				return $message->getMailboxId() === $mailbox->getId();
+			});
+
+			if (empty($filteredMessages)) {
+				continue;
+			}
+
+			// Check for accounts or mailboxes that no longer exist,
+			// no processing for drafts, sent items, junk or archive
+			if ($account === null
+				|| $account->getMailAccount()->getTrashMailboxId() === $mailbox->getId()
+				|| $account->getMailAccount()->getSentMailboxId() === $mailbox->getId()
+				|| $account->getMailAccount()->getDraftsMailboxId() === $mailbox->getId()
+				|| $mailbox->isSpecialUse(\Horde_Imap_Client::SPECIALUSE_ARCHIVE)
+			) {
+				$processedMessages = array_map(function (Message $message) {
+					$message->setImipProcessed(true);
+					return $message;
+				}, $filteredMessages); // Silently drop from passing to DAV and mark as processed, so we won't run into these messages again.
+				$this->messageMapper->updateImipData(...$processedMessages);
+				continue;
+			}
+
+			try {
+				$imapMessages = $this->mailManager->getImapMessagesForScheduleProcessing($account, $mailbox, array_map(function ($message) {
+					return $message->getUid();
+				}, $filteredMessages));
+			} catch (ServiceException $e) {
+				$this->logger->error('Could not get IMAP messages form IMAP server', ['exception' => $e]);
+				continue;
+			}
+
+			foreach ($filteredMessages as $message) {
+				/** @var IMAPMessage $imapMessage */
+				$imapMessage = current(array_filter($imapMessages, function (IMAPMessage $imapMessage) use ($message) {
+					return $message->getUid() === $imapMessage->getUid();
+				}));
+				if (empty($imapMessage->scheduling)) {
+					// No scheduling info, maybe the DB is wrong
+					$message->setImipError(true);
+					continue;
+				}
+
+				$principalUri = 'principals/users/' . $account->getUserId();
+				$sender = $imapMessage->getFrom()->first()->getEmail();
+				$recipient = $account->getEmail();
+				foreach ($imapMessage->scheduling as $schedulingInfo) { // an IMAP message could contain more than one iMIP object
+					if ($schedulingInfo['method'] === 'REPLY') {
+						$processed = $this->calendarManager->handleIMipReply($principalUri, $sender, $recipient, $schedulingInfo['contents']);
+						$message->setImipProcessed($processed);
+						$message->setImipError(!$processed);
+					} elseif ($schedulingInfo['method'] === 'CANCEL') {
+						$replyTo = $imapMessage->getReplyTo()->first();
+						$replyTo = !empty($replyTo) ? $replyTo->getEmail() : null;
+						$processed = $this->calendarManager->handleIMipCancel($principalUri, $sender, $replyTo, $recipient, $schedulingInfo['contents']);
+						$message->setImipProcessed($processed);
+						$message->setImipError(!$processed);
+					}
+				}
+			}
+			$this->messageMapper->updateImipData(...$filteredMessages);
+		}
+	}
+}
diff --git a/lib/Service/MailManager.php b/lib/Service/MailManager.php
index 883d98554..cbe5229d4 100644
--- a/lib/Service/MailManager.php
+++ b/lib/Service/MailManager.php
@@ -26,6 +26,7 @@ namespace OCA\Mail\Service;
 use Horde_Imap_Client;
 use Horde_Imap_Client_Exception;
 use Horde_Imap_Client_Exception_NoSupportExtension;
+use Horde_Imap_Client_Ids;
 use Horde_Imap_Client_Socket;
 use OCA\Mail\Account;
 use OCA\Mail\Contracts\IMailManager;
@@ -193,6 +194,35 @@ class MailManager implements IMailManager {
 		}
 	}
 
+	/**
+	 * @param Account $account
+	 * @param Mailbox $mailbox
+	 * @param int[] $uids
+	 * @return IMAPMessage[]
+	 * @throws ServiceException
+	 */
+	public function getImapMessagesForScheduleProcessing(Account $account,
+		Mailbox $mailbox,
+		array $uids): array {
+		$client = $this->imapClientFactory->getClient($account);
+		try {
+			return $this->imapMessageMapper->findByIds(
+				$client,
+				$mailbox->getName(),
+				new Horde_Imap_Client_Ids($uids),
+				true
+			);
+		} catch (Horde_Imap_Client_Exception $e) {
+			throw new ServiceException(
+				'Could not load messages: ' . $e->getMessage(),
+				(int)$e->getCode(),
+				$e
+			);
+		} finally {
+			$client->logout();
+		}
+	}
+
 	public function getThread(Account $account, string $threadRootId): array {
 		return $this->dbMessageMapper->findThread($account, $threadRootId);
 	}
diff --git a/lib/Service/PreprocessingService.php b/lib/Service/PreprocessingService.php
new file mode 100644
index 000000000..e37a51ad2
--- /dev/null
+++ b/lib/Service/PreprocessingService.php
@@ -0,0 +1,85 @@
+<?php
+
+declare(strict_types=1);
+/*
+ * *
+ *  * {$app} App
+ *  *
+ *  * @copyright 2022 Anna Larch <anna.larch@gmx.net>
+ *  *
+ *  * @author Anna Larch <anna.larch@gmx.net>
+ *  *
+ *  * This library is free software; you can redistribute it and/or
+ *  * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ *  * License as published by the Free Software Foundation; either
+ *  * version 3 of the License, or any later version.
+ *  *
+ *  * This library is distributed in the hope that it will be useful,
+ *  * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+ *  *
+ *  * You should have received a copy of the GNU Affero General Public
+ *  * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ *  *
+ *
+ */
+
+namespace OCA\Mail\Service;
+
+use OCA\Mail\Account;
+use OCA\Mail\Db\Mailbox;
+use OCA\Mail\Db\MailboxMapper;
+use OCA\Mail\Db\MessageMapper;
+use OCA\Mail\IMAP\PreviewEnhancer;
+use Psr\Log\LoggerInterface;
+
+class PreprocessingService {
+	private MailboxMapper $mailboxMapper;
+	private MessageMapper $messageMapper;
+	private LoggerInterface $logger;
+	private PreviewEnhancer $previewEnhancer;
+
+	public function __construct(
+		MessageMapper $messageMapper,
+		LoggerInterface $logger,
+		MailboxMapper $mailboxMapper,
+		PreviewEnhancer $previewEnhancer
+	) {
+		$this->messageMapper = $messageMapper;
+		$this->logger = $logger;
+		$this->mailboxMapper = $mailboxMapper;
+		$this->previewEnhancer = $previewEnhancer;
+	}
+
+	public function process(int $limitTimestamp, Account $account): void {
+		$mailboxes = $this->mailboxMapper->findAll($account);
+		if (empty($mailboxes)) {
+			$this->logger->debug('No mailboxes found.');
+			return;
+		}
+		$mailboxIds = array_unique(array_map(function (Mailbox $mailbox) {
+			return $mailbox->getId();
+		}, $mailboxes));
+
+
+		$messages = $this->messageMapper->getUnanalyzed($limitTimestamp, $mailboxIds);
+		if (empty($messages)) {
+			$this->logger->debug('No structure data to analyse.');
+			return;
+		}
+
+		foreach ($mailboxes as $mailbox) {
+			$filteredMessages = array_filter($messages, function ($message) use ($mailbox) {
+				return $message->getMailboxId() === $mailbox->getId();
+			});
+
+			if (empty($filteredMessages)) {
+				continue;
+			}
+
+			$processedMessages = $this->previewEnhancer->process($account, $mailbox, $filteredMessages);
+			$this->logger->debug('Processed ' . count($processedMessages) . ' messages for structure data for mailbox ' . $mailbox->getId());
+		}
+	}
+}
diff --git a/tests/Unit/Job/PreviewEnhancementProcessingJobTest.php b/tests/Unit/Job/PreviewEnhancementProcessingJobTest.php
new file mode 100644
index 000000000..e9dfd5755
--- /dev/null
+++ b/tests/Unit/Job/PreviewEnhancementProcessingJobTest.php
@@ -0,0 +1,172 @@
+<?php
+/*
+ * *
+ *  * Mail App
+ *  *
+ *  * @copyright 2022 Anna Larch <anna.larch@gmx.net>
+ *  *
+ *  * @author Anna Larch <anna.larch@gmx.net>
+ *  *
+ *  * This library is free software; you can redistribute it and/or
+ *  * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ *  * License as published by the Free Software Foundation; either
+ *  * version 3 of the License, or any later version.
+ *  *
+ *  * This library is distributed in the hope that it will be useful,
+ *  * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+ *  *
+ *  * You should have received a copy of the GNU Affero General Public
+ *  * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ *  *
+ *
+ */
+
+namespace OCA\Mail\Tests\Unit\Job;
+
+use OCA\Mail\Account;
+use OCA\Mail\BackgroundJob\PreviewEnhancementProcessingJob;
+use OCA\Mail\Db\MailAccount;
+use OCA\Mail\Service\AccountService;
+use OCA\Mail\Service\PreprocessingService;
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\IJobList;
+use OCP\IUser;
+use OCP\IUserManager;
+use PHPUnit\Framework\MockObject\MockObject;
+use ChristophWurst\Nextcloud\Testing\TestCase;
+use Psr\Log\LoggerInterface;
+
+class PreviewEnhancementProcessingJobTest extends TestCase {
+	/** @var ITimeFactory|ITimeFactory&MockObject|MockObject  */
+	private $time;
+
+	/** @var IUserManager|IUserManager&MockObject|MockObject  */
+	private $manager;
+
+	/** @var AccountService|AccountService&MockObject|MockObject  */
+	private $accountService;
+
+	/** @var PreprocessingService|PreprocessingService&MockObject|MockObject  */
+	private $preprocessingService;
+
+	/** @var MockObject|LoggerInterface|LoggerInterface&MockObject  */
+	private $logger;
+
+	/** @var IJobList|IJobList&MockObject|MockObject  */
+	private $jobList;
+
+	/** @var int[]  */
+	private static $argument;
+
+	public function setUp(): void {
+		parent::setUp();
+		$this->time = $this->createMock(ITimeFactory::class);
+		$this->manager = $this->createMock(IUserManager::class);
+		$this->accountService = $this->createMock(AccountService::class);
+		$this->preprocessingService = $this->createMock(PreprocessingService::class);
+		$this->logger = $this->createMock(LoggerInterface::class);
+		$this->jobList = $this->createMock(IJobList::class);
+		$this->job = new PreviewEnhancementProcessingJob(
+			$this->time,
+			$this->manager,
+			$this->accountService,
+			$this->preprocessingService,
+			$this->logger,
+			$this->jobList
+		);
+
+		self::$argument = ['accountId' => 1];
+	}
+
+	public function testNoAccount(): void {
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->with(self::$argument['accountId'])
+			->willThrowException(new DoesNotExistException('Account does not exist'));
+		$this->logger->expects(self::once())
+			->method('debug');
+		$this->jobList->expects(self::once())
+			->method('remove');
+
+		$this->job->run(self::$argument);
+	}
+
+	public function testNoUser(): void {
+		$mailAccount = new MailAccount();
+		$mailAccount->setUserId(1);
+		$account = new Account($mailAccount);
+
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->with(self::$argument['accountId'])
+			->willReturn($account);
+		$this->manager->expects(self::once())
+			->method('get')
+			->with($account->getUserId())
+			->willReturn(null);
+		$this->logger->expects(self::once())
+			->method('debug');
+
+		$this->job->run(self::$argument);
+	}
+
+	public function testProvisionedNoPassword(): void {
+		$mailAccount = new MailAccount();
+		$mailAccount->setUserId(1);
+		$mailAccount->setProvisioningId(1);
+		$mailAccount->setInboundPassword(null);
+		$account = new Account($mailAccount);
+		$user = $this->createMock(IUser::class);
+		$user->setEnabled();
+
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->with(self::$argument['accountId'])
+			->willReturn($account);
+		$this->manager->expects(self::once())
+			->method('get')
+			->with($account->getUserId())
+			->willReturn($user);
+		$user->expects(self::once())
+			->method('isEnabled')
+			->willReturn(true);
+		$this->logger->expects(self::once())
+			->method('info');
+
+		$this->job->run(self::$argument);
+	}
+
+	public function testProcessing(): void {
+		$mailAccount = new MailAccount();
+		$mailAccount->setUserId(1);
+		$account = new Account($mailAccount);
+		$time = time();
+		$user = $this->createMock(IUser::class);
+		$user->setEnabled();
+
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->with(self::$argument['accountId'])
+			->willReturn($account);
+		$this->manager->expects(self::once())
+			->method('get')
+			->with($account->getUserId())
+			->willReturn($user);
+		$user->expects(self::once())
+			->method('isEnabled')
+			->willReturn(true);
+		$this->time->expects(self::once())
+			->method('getTime')
+			->willReturn($time);
+		$this->preprocessingService->expects(self::once())
+			->method('process')
+			->with(($time - (60 * 60 * 24 * 14)), $account);
+		$this->logger->expects(self::never())
+			->method('error');
+
+		$this->job->run(self::$argument);
+	}
+}
diff --git a/tests/Unit/Service/IMipServiceTest.php b/tests/Unit/Service/IMipServiceTest.php
new file mode 100644
index 000000000..2f39b5b2c
--- /dev/null
+++ b/tests/Unit/Service/IMipServiceTest.php
@@ -0,0 +1,458 @@
+<?php
+/*
+ * *
+ *  * {$app} App
+ *  *
+ *  * @copyright 2022 Anna Larch <anna.larch@gmx.net>
+ *  *
+ *  * @author Anna Larch <anna.larch@gmx.net>
+ *  *
+ *  * This library is free software; you can redistribute it and/or
+ *  * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ *  * License as published by the Free Software Foundation; either
+ *  * version 3 of the License, or any later version.
+ *  *
+ *  * This library is distributed in the hope that it will be useful,
+ *  * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+ *  *
+ *  * You should have received a copy of the GNU Affero General Public
+ *  * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ *  *
+ *
+ */
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2022 Anna Larch <anna.larch@gm.net>
+ *
+ * @author 2022 Anna Larch <anna.larch@gm.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\Mail\Tests\Service;
+
+use ChristophWurst\Nextcloud\Testing\TestCase;
+use OCA\Mail\Account;
+use OCA\Mail\Address;
+use OCA\Mail\AddressList;
+use OCA\Mail\Db\MailAccount;
+use OCA\Mail\Db\MailboxMapper;
+use OCA\Mail\Db\Message;
+use OCA\Mail\Db\MessageMapper;
+use OCA\Mail\Db\Mailbox;
+use OCA\Mail\Exception\ServiceException;
+use OCA\Mail\Model\IMAPMessage;
+use OCA\Mail\Service\AccountService;
+use OCA\Mail\Service\IMipService;
+use OCA\Mail\Service\MailManager;
+use OCP\Calendar\IManager;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Log\LoggerInterface;
+
+class IMipServiceTest extends TestCase {
+	/** @var MailboxMapper|MockObject */
+	private $mailboxMapper;
+
+	/** @var MessageMapper|MockObject */
+	private $messageMapper;
+
+	/** @var AccountService|MockObject */
+	private $accountService;
+
+	/** @var MailManager|MockObject  */
+	private $mailManager;
+
+	/** @var MockObject|LoggerInterface  */
+	private $logger;
+
+	private IMipService $service;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		// iMIP is NC25+
+		if (!method_exists(IManager::class, 'handleImipReply')) {
+			self::markTestIncomplete();
+		}
+
+
+		$this->accountService = $this->createMock(AccountService::class);
+		$this->calendarManager = $this->createMock(IManager::class);
+		$this->mailboxMapper = $this->createMock(MailboxMapper::class);
+		$this->logger = $this->createMock(LoggerInterface::class);
+		$this->mailManager = $this->createMock(MailManager::class);
+		$this->messageMapper = $this->createMock(MessageMapper::class);
+
+		$this->service = new IMipService(
+			$this->accountService,
+			$this->calendarManager,
+			$this->logger,
+			$this->mailboxMapper,
+			$this->mailManager,
+			$this->messageMapper
+		);
+	}
+
+	public function testNoSchedulingInformation(): void {
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([]);
+		$this->logger->expects(self::once())
+			->method('info');
+		$this->mailboxMapper->expects(self::never())
+			->method('findById');
+		$this->accountService->expects(self::never())
+			->method('findById');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipReply');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+		$this->messageMapper->expects(self::never())
+			->method('updateImipData');
+
+		$this->service->process();
+	}
+
+	public function testIsSpecialUse(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$mailbox->setSpecialUse('["sent"]');
+		$mailAccount = new MailAccount();
+		$mailAccount->setDraftsMailboxId(100);
+		$account = new Account($mailAccount);
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->with($message->getMailboxId())
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->with($mailbox->getAccountId())
+			->willReturn($account);
+		$this->messageMapper->expects(self::once())
+			->method('updateImipData');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipReply');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+
+		$this->service->process();
+	}
+
+	public function testIsArchive(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$mailbox->setSpecialUse('["archive"]');
+		$mailAccount = new MailAccount();
+		$account = new Account($mailAccount);
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->with($message->getMailboxId())
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->with($mailbox->getAccountId())
+			->willReturn($account);
+		$this->messageMapper->expects(self::once())
+			->method('updateImipData');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipReply');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+
+		$this->service->process();
+	}
+
+	public function testNoSchedulingInfo(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$account = $this->createConfiguredMock(Account::class, [
+			'getId' => 200,
+			'getEmail' => 'dimitrius@stardew-science.com'
+		]);
+		$imapMessage = $this->createConfiguredMock(IMAPMessage::class, [
+			'getUid' => 1
+		]);
+		$imapMessage->scheduling = [];
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->willReturn($account);
+		$this->mailManager->expects(self::once())
+			->method('getImapMessagesForScheduleProcessing')
+			->with($account, $mailbox, [$message->getUid()])
+			->willReturn([$imapMessage]);
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipReply');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+		$this->messageMapper->expects(self::once())
+			->method('updateImipData')
+			->with($message);
+
+		$this->service->process();
+	}
+
+	public function testImapConnectionServiceException(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$account = $this->createConfiguredMock(Account::class, [
+			'getId' => 200,
+			'getEmail' => 'dimitrius@stardew-science.com'
+		]);
+		$imapMessage = $this->createConfiguredMock(IMAPMessage::class, [
+			'getUid' => 1
+		]);
+		$imapMessage->scheduling = [];
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->willReturn($account);
+		$this->mailManager->expects(self::once())
+			->method('getImapMessagesForScheduleProcessing')
+			->willThrowException(new ServiceException());
+		$this->logger->expects(self::once())
+			->method('error');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipReply');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+		$this->messageMapper->expects(self::never())
+			->method('updateImipData');
+
+		$this->service->process();
+	}
+
+	public function testIsRequest(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$mailAccount = new MailAccount();
+		$mailAccount->setId(200);
+		$account = new Account($mailAccount);
+		$imapMessage = $this->createMock(IMAPMessage::class);
+		$imapMessage->scheduling[] = ['method' => 'REQUEST'];
+		$addressList = $this->createMock(AddressList::class);
+		$address = $this->createMock(Address::class);
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->willReturn($account);
+		$this->mailManager->expects(self::once())
+			->method('getImapMessagesForScheduleProcessing')
+			->with($account, $mailbox, [$message->getUid()])
+			->willReturn([$imapMessage]);
+		$imapMessage->expects(self::once())
+			->method('getUid')
+			->willReturn(1);
+		$imapMessage->expects(self::once())
+			->method('getFrom')
+			->willReturn($addressList);
+		$addressList->expects(self::once())
+			->method('first')
+			->willReturn($address);
+		$address->expects(self::once())
+			->method('getEmail')
+			->willReturn('pam@stardew-bus-company.com');
+		$this->logger->expects(self::never())
+			->method('info');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipReply');
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+		$this->messageMapper->expects(self::never())
+			->method('updateBulk');
+
+		$this->service->process();
+	}
+
+	public function testIsReply(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$mailAccount = new MailAccount();
+		$mailAccount->setId(200);
+		$mailAccount->setEmail('vincent@stardew-valley.edu');
+		$mailAccount->setUserId('vincent');
+		$account = new Account($mailAccount);
+		$imapMessage = $this->createMock(IMAPMessage::class);
+		$imapMessage->scheduling[] = ['method' => 'REPLY', 'contents' => 'VCARD'];
+		$addressList = $this->createMock(AddressList::class);
+		$address = $this->createMock(Address::class);
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->willReturn($account);
+		$this->mailManager->expects(self::once())
+			->method('getImapMessagesForScheduleProcessing')
+			->with($account, $mailbox, [$message->getUid()])
+			->willReturn([$imapMessage]);
+		$imapMessage->expects(self::once())
+			->method('getUid')
+			->willReturn(1);
+		$this->logger->expects(self::never())
+			->method('info');
+		$imapMessage->expects(self::once())
+			->method('getFrom')
+			->willReturn($addressList);
+		$addressList->expects(self::once())
+			->method('first')
+			->willReturn($address);
+		$address->expects(self::once())
+			->method('getEmail')
+			->willReturn('pam@stardew-bus-service.com');
+		$imapMessage->expects(self::never())
+			->method('getInReplyTo')
+			->willReturn($addressList);
+		$this->calendarManager->expects(self::once())
+			->method('handleIMipReply')
+			->with('principals/users/vincent',
+				'pam@stardew-bus-service.com',
+				$account->getEmail(),
+				$imapMessage->scheduling[0]['contents']);
+		$this->calendarManager->expects(self::never())
+			->method('handleIMipCancel');
+		$this->messageMapper->expects(self::once())
+			->method('updateImipData');
+
+		$this->service->process();
+	}
+
+	public function testIsCancel(): void {
+		$message = new Message();
+		$message->setImipMessage(true);
+		$message->setUid(1);
+		$message->setMailboxId(100);
+		$mailbox = new Mailbox();
+		$mailbox->setId(100);
+		$mailbox->setAccountId(200);
+		$mailAccount = new MailAccount();
+		$mailAccount->setId(200);
+		$mailAccount->setEmail('vincent@stardew-valley.edu');
+		$mailAccount->setUserId('vincent');
+		$account = new Account($mailAccount);
+		$imapMessage = $this->createMock(IMAPMessage::class);
+		$imapMessage->scheduling[] = ['method' => 'CANCEL', 'contents' => 'VCARD'];
+		$addressList = $this->createMock(AddressList::class);
+		$address = $this->createMock(Address::class);
+
+		$this->messageMapper->expects(self::once())
+			->method('findIMipMessagesAscending')
+			->willReturn([$message]);
+		$this->mailboxMapper->expects(self::once())
+			->method('findById')
+			->willReturn($mailbox);
+		$this->accountService->expects(self::once())
+			->method('findById')
+			->willReturn($account);
+		$this->mailManager->expects(self::once())
+			->method('getImapMessagesForScheduleProcessing')
+			->with($account, $mailbox, [$message->getUid()])
+			->willReturn([$imapMessage]);
+		$imapMessage->expects(self::once())
+			->method('getUid')
+			->willReturn(1);
+		$this->logger->expects(self::never())
+			->method('info');
+		$imapMessage->expects(self::once())
+			->method('getFrom')
+			->willReturn($addressList);
+		$addressList->expects(self::once())
+			->method('first')
+			->willReturn($address);
+		$address->expects(self::once())
+			->method('getEmail')
+			->willReturn('pam@stardew-bus-service.com');
+		$imapMessage->expects(self::once())
+			->method('getReplyTo')
+			->willReturn(new AddressList([]));
+		$this->calendarManager->expects(self::once())
+			->method('handleIMipCancel')
+			->with('principals/users/vincent',
+				'pam@stardew-bus-service.com',
+				null,
+				$account->getEmail(),
+				$imapMessage->scheduling[0]['contents']
+			);
+		$this->messageMapper->expects(self::once())
+			->method('updateImipData');
+
+		$this->service->process();
+	}
+}
diff --git a/tests/Unit/Service/PreprocessingServiceTest.php b/tests/Unit/Service/PreprocessingServiceTest.php
new file mode 100644
index 000000000..e181d9e0b
--- /dev/null
+++ b/tests/Unit/Service/PreprocessingServiceTest.php
@@ -0,0 +1,130 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright 2022 Anna Larch <anna.larch@gm.net>
+ *
+ * @author 2022 Anna Larch <anna.larch@gm.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\Mail\Tests\Service;
+
+use ChristophWurst\Nextcloud\Testing\TestCase;
+use OCA\Mail\Account;
+use OCA\Mail\Db\MailAccount;
+use OCA\Mail\Db\MailboxMapper;
+use OCA\Mail\Db\Message;
+use OCA\Mail\Db\MessageMapper;
+use OCA\Mail\Db\Mailbox;
+use OCA\Mail\IMAP\PreviewEnhancer;
+use OCA\Mail\Service\PreprocessingService;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Log\LoggerInterface;
+
+class PreprocessingServiceTest extends TestCase {
+	/** @var MailboxMapper|MockObject */
+	private $mailboxMapper;
+
+	/** @var MessageMapper|MockObject */
+	private $messageMapper;
+
+	/** @var MockObject|LoggerInterface  */
+	private $logger;
+
+	/** @var MockObject|PreviewEnhancer */
+	private $previewEnhancer;
+
+	private PreprocessingService $service;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->mailboxMapper = $this->createMock(MailboxMapper::class);
+		$this->logger = $this->createMock(LoggerInterface::class);
+		$this->messageMapper = $this->createMock(MessageMapper::class);
+		$this->previewEnhancer = $this->createMock(PreviewEnhancer::class);
+
+		$this->service = new PreprocessingService(
+			$this->messageMapper,
+			$this->logger,
+			$this->mailboxMapper,
+			$this->previewEnhancer
+		);
+	}
+
+	public function testNoMailboxes(): void {
+		$account = new Account(new MailAccount());
+		$timestamp = 0;
+
+		$this->mailboxMapper->expects(self::once())
+			->method('findAll')
+			->with($account)
+			->willReturn([]);
+		$this->messageMapper->expects(self::never())
+			->method('getUnanalyzed');
+		$this->previewEnhancer->expects(self::never())
+			->method('process');
+
+		$this->service->process($timestamp, $account);
+	}
+
+	public function testNoUnanalysed(): void {
+		$account = new Account(new MailAccount());
+		$timestamp = 0;
+		$mailbox = new Mailbox();
+		$mailbox->setId(1);
+
+		$this->mailboxMapper->expects(self::once())
+			->method('findAll')
+			->with($account)
+			->willReturn([$mailbox]);
+		$this->messageMapper->expects(self::once())
+			->method('getUnanalyzed')
+			->with($timestamp, [$mailbox->getId()])
+			->willReturn([]);
+		$this->previewEnhancer->expects(self::never())
+			->method('process');
+
+		$this->service->process($timestamp, $account);
+	}
+
+	public function testProcessing(): void {
+		$account = new Account(new MailAccount());
+		$timestamp = 0;
+		$mailbox = new Mailbox();
+		$mailbox->setId(1);
+		$message = new Message();
+		$message->setMailboxId($mailbox->getId());
+
+		$this->mailboxMapper->expects(self::once())
+			->method('findAll')
+			->with($account)
+			->willReturn([$mailbox]);
+		$this->messageMapper->expects(self::once())
+			->method('getUnanalyzed')
+			->with($timestamp, [$mailbox->getId()])
+			->willReturn([$message]);
+		$this->previewEnhancer->expects(self::once())
+			->method('process')
+			->with($account, $mailbox, [$message])
+			->willReturn([$message]);
+
+		$this->service->process($timestamp, $account);
+	}
+}