In the Google Cloud Platform documentation I read that it has restrictions on sending emails from VMs created on it.
However, I need create a VM with Exim that will only receive emails via SMTP. Does Google Cloud Platform allow having a VM for this purpose?
I searched the documentation and found nothing.
>Solution :
Google Cloud allows ingress on port 25 which means you can implement an SMTP server for the receipt of mail.
Egress on port 25 will be blocked.
Just make sure you understand what SMTP is, which is server-to-server mail transfer. Since that means port 25 must be open to the world, you will be hit with a massive number of spam connection attempts. You might find it very expensive paying for that traffic.
You mention: But external users send emails to us. No, they won’t. Users do not send mail over port 25 unless you have written an application to do so. For the most part, port 25 is universally blocked around the world. Most consumer ISPs block port 25 ingress and egress. Commercial companies usually must apply for an exemption to use port 25 for egress. For an end user to send mail to you on port 25 they must use egress.
I strongly recommend that you rethink your strategy.