ENGCOM-6034: add encoding to TransportBuilder #24906

 - Merge Pull Request #24906 from elvinristi/magento2:fix/issue-24902--email-headers-encoding
 - Merged commits:
   1. 95878b7
   2. 0b9013e
   3. 78db864

Author: magento-engcom-team

dev/tests/integration/testsuite/Magento/Customer/Controller/AccountTest.php

@@ -769,9 +769,21 @@ public function testConfirmationEmailWithSpecialCharacters(): void
         $message = $this->transportBuilderMock->getSentMessage();
         $rawMessage = $message->getRawMessage();
 
-        $this->assertContains('To: John Smith <' . $email . '>', $rawMessage);
+        /** @var \Zend\Mime\Part $messageBodyPart */
+        $messageBodyParts = $message->getBody()->getParts();
+        $messageBodyPart = reset($messageBodyParts);
+        $messageEncoding = $messageBodyPart->getCharset();
+        $name = 'John Smith';
+
+        if (strtoupper($messageEncoding) !== 'ASCII') {
+            $name = \Zend\Mail\Header\HeaderWrap::mimeEncodeValue($name, $messageEncoding);
+        }
+
+        $nameEmail = sprintf('%s <%s>', $name, $email);
+
+        $this->assertContains('To: ' . $nameEmail, $rawMessage);
 
-        $content = $message->getBody()->getParts()[0]->getRawContent();
+        $content = $messageBodyPart->getRawContent();
         $confirmationUrl = $this->getConfirmationUrlFromMessageContent($content);
         $this->setRequestInfo($confirmationUrl, 'confirm');
         $this->clearCookieMessagesList();

lib/internal/Magento/Framework/Mail/Template/TransportBuilder.php

@@ -377,6 +377,7 @@ protected function prepareMessage()
     {
         $template = $this->getTemplate();
         $content = $template->processTemplate();
+
         switch ($template->getType()) {
             case TemplateTypesInterface::TYPE_TEXT:
                 $part['type'] = MimeInterface::TYPE_TEXT;
@@ -391,7 +392,10 @@ protected function prepareMessage()
                     new Phrase('Unknown template type')
                 );
         }
+
+        /** @var \Magento\Framework\Mail\MimePartInterface $mimePart */
         $mimePart = $this->mimePartInterfaceFactory->create(['content' => $content]);
+        $this->messageData['encoding'] = $mimePart->getCharset();
         $this->messageData['body'] = $this->mimeMessageInterfaceFactory->create(
             ['parts' => [$mimePart]]
         );
@@ -400,6 +404,7 @@ protected function prepareMessage()
             (string)$template->getSubject(),
             ENT_QUOTES
         );
+
         $this->message = $this->emailMessageInterfaceFactory->create($this->messageData);
 
         return $this;