Recently I switch my host provider to Google Cloud Platform. Everything works great until I found outgoing mail traffic is blocked by Google.
Google Compute Engine does not allow outbound connections on ports 25, 465, and 587
See Sending Email from an Instance | Compute Engine Documentation | Google Cloud for detail.
Google advises using SendGrid, Mailgun, or Mailjet. However, since I didn’t see any Mailgun plugin for Discourse (two repo on GitHub indeed, but one hasn’t been updated since 2015, and the other even breaks the rebuild of Discourse), I formerly use SMTP to send emails via Mailgun, but this way has been blocked by Google. So my site’s email system is totally breaking down.
Is there any solution?