contact us page submit but email not received

Question

when contact us page submit but email not received but messages display

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in debug.log I get this error.

main.CRITICAL: Unable to send mail: Unknown error {"exception":"[object] (Magento\\Framework\\Exception\\MailException(code: 0): Unable to send mail: Unknown error at /public_html/vendor/magento/module-email/Model/Transport.php:104, Zend\\Mail\\Transport\\Exception\\RuntimeException(code: 0): Unable to send mail: Unknown error at /public_html/vendor/zendframework/zend-mail/src/Transport/Sendmail.php:305)"} []

in exception.log I get this error.

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

Answer 1

A 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;

https://github.com/magento/magento2/issues/24902