magento2: M2.3.3 breaks email sending when name contains non-ASCII char

Preconditions (*)

1. Magento M2.3.3

Steps to reproduce (*)

1. Open registration or contact us page
2. Enter correct details and as a name include some non-ASCII char, i.e some õäöü

Expected result (*)

1. After registration user receives email
2. No errors exist in var/log/exception.log

Actual result (*)

1. User doesn’t receive email
2. Log includes Exception with message Invalid header value detected

[2019-10-07 11:33:57] report.CRITICAL: Invalid header value detected {"exception":"[object] (Magento\\Framework\\Exception\\MailException(code: 0): Invalid header value detected at vendor/magento/module-email/Model/Transport.php:104, Zend\\Mail\\Header\\Exception\\RuntimeException(code: 0): Invalid header value detected at vendor/zendframework/zend-mail/src/Header/HeaderValue.php:112)"}

Reasons:

• ZF2 conforms only to RFC 2822

Potential fix is to add encoding in vendor/magento/framework/Mail/Template/TransportBuilder.php

--- vendor/magento/framework/Mail/Template/TransportBuilder.php.org	2019-10-07 17:16:16.946791204 +0200
+++ vendor/magento/framework/Mail/Template/TransportBuilder.php	2019-10-07 17:16:44.243320666 +0200
@@ -402,6 +402,7 @@
             (string)$template->getSubject(),
             ENT_QUOTES
         );
+        $this->messageData['encoding'] = $mimePart->getCharset();
         $this->message = $this->emailMessageInterfaceFactory->create($this->messageData);

         return $this;