Emails not sending on M2.3.3 due to backward-incompatible changes

[jaxtheking]

This may strengthens the case I made here (#5) for the need of a Send Test Email function...
M2.3.3 introduced a backward-incompatible change by introducing the new EmailMessageInterface. You can read the relevant bit of the release notes here:

Therefore, the sending of emails in M2.3.3 results in the following error:
Fatal error: Uncaught TypeError: Argument 1 passed to Ebizmarts\MandrillSmtp\Model\Transport\Smtp::sendMessage() must implement interface Magento\Framework\Mail\MessageInterface, instance of Magento\Framework\Mail\EmailMessage given, called in /vendor/ebizmarts/magento2-mandrillsmtp/Plugin/Mail/TransportPlugin.php on line 42 and defined in /vendor/ebizmarts/magento2-mandrillsmtp/Model/Transport/Smtp.php:48

Stack trace:
#0 /vendor/ebizmarts/magento2-mandrillsmtp/Plugin/Mail/TransportPlugin.php(42): Ebizmarts\MandrillSmtp\Model\Transport\Smtp->sendMessage(Object(Magento\Framework\Mail\EmailMessage))

#1 /vendor/magento/framework/Interception/Interceptor.php(135): Ebizmarts\MandrillSmtp\Plugin\Mail\TransportPlugin->aroundSendMessage(Object(Magento\Email\Model\Transport\Interceptor), Object(Closure))

#2 /dev/vendor/magento/module-email/Model/Mail/TransportInterfacePlugin.php(48): Mag in /dev/vendor/ebizmarts/magento2-mandrillsmtp/Model/Transport/Smtp.php on line 48

To fix it, we just need to change all MessageInterface references (only 3) to EmailMessageInterface in /vendor/ebizmarts/magento2-mandrillsmtp/Model/Transport/Smtp.php, with no further changes needed.

I hope this helps.
Regards,
Luca

[gonzaloebiz]

Thanks @jaxtheking