I'm looking to run a mail server on a Google Compute Engine instance, and have discovered Google's blockage of port 25, 465, and 587. I'll probably use Mailjet for outgoing mail. Anyone found a good solution for incoming mail?Answer1:
Email messages sent to your app are implemented as HTTP requests containing MIME data. To process incoming email messages, you associate email addresses with script handlers in your app configuration, then include the handlers in your app's code.
The link below is for python but there is no restriction on language. <a href="https://cloud.google.com/appengine/docs/standard/python/mail/receiving-mail-with-mail-api" rel="nofollow">https://cloud.google.com/appengine/docs/standard/python/mail/receiving-mail-with-mail-api</a>