Timeout when connecting to remote imap server

Solution 1:

I see that this post has been created 2 years ago, and I'd like to ask if the issue has been solved.

For the issue, I'd like to clarify, that port 25 is blocked for security reasons. https://cloud.google.com/compute/docs/tutorials/sending-mail#using_standard_email_ports

This is an external tutorial about how to create your configuration on GCP: https://blog.cyberpanel.net/2018/05/30/setup-external-smtp-on-google-cloud-platform-gcp/

I recommend you to ensure firewall rules are ok and you're using on the Instance the VPC that you opened the Firewall Rules, change the port 25 and check routes on GCP.