Replace Zend Mail with PHPMailer (#15891)

* require composer package phpmailer/phpmailer

* change mail class to use phpmailer instead of Zend_Mail

* removes Zend_Mail and Zend_Mime

* submodule

* fix tests

* enable smtp debug for test mail command

* fix embedded images

* set language for phpmailer

* apply some review feedback

* removes Zend_Validate (#15907)

* don't inline file without cid

* submodule update

* fix test

* decouples Mail class from PHPMailer and moves sending mails to new transport layer

* submodule

* cleanup

* unset xmailer header

* simplify mail attachment handling

* adds methods to add bcc recipients

* change implementation of setReplyTo

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/PHPUnit/Integration/ReleaseCheckListTest.php b/tests/PHPUnit/Integration/ReleaseCheckListTest.php
index 1ab738ddc1..74e4886450 100644
--- a/tests/PHPUnit/Integration/ReleaseCheckListTest.php
+++ b/tests/PHPUnit/Integration/ReleaseCheckListTest.php
@@ -873,6 +873,7 @@ class ReleaseCheckListTest extends \PHPUnit\Framework\TestCase
             }
 
             if(strpos($file, 'vendor/php-di/php-di/website/') !== false
+                || strpos($file, 'vendor/phpmailer/phpmailer/language/') !== false
                 || strpos($file, 'plugins/VisitorGenerator/vendor/fzaninotto/faker/src/Faker/Provider/') !== false) {
                 continue;
             }