It is not possible to send email from a Plesk server on Google Cloud. Incoming mail is received successfully, but outgoing messages are stuck in the queue.
How to send email from a Plesk server on Google Cloud?
By default, Google Compute Engine blocks 25, 465 and 587 SMTP ports and does not allow outbound connections on them. Instances still can receive emails, while sending emails from blocked ports is not allowed.
To configure sending emails, use one of the following solutions:
- Use one of Compute Engine’s third-party partners (SendGrid, Mailgun, and Mailjet) to set up and send emails through their servers. All these services have a free tier for the Google Cloud customers - 12,000 emails/month on SendGrid, 30,000 emails/month on Mailgun and 25,000 emails/month on Mailjet.
- Use Google Apps account to set up a relay service to send emails through Google Apps.
Both solutions are described in the Google Cloud documentation https://cloud.google.com/compute/docs/tutorials/sending-mail/