SMTP relay for GCP hosting

[Matt Stevenson]

Hi All

We are planning to host WHM in Google and so require SMTP relay.
I've read some brilliant and not so brilliant articles on here, that have helped me.

Google requires instances to send mail via relay.
Sending Email from an Instance  |  Compute Engine Documentation  |  Google Cloud Platform

So far I have looked at :

Smart host.
Exim Configuration Manager - Basic Editor - Documentation - cPanel Documentation

We trialled exim with this config.
Exim 4 configuration for SendGrid - SendGrid Documentation | SendGrid

This would send emails but could not receive.

Wonder what other options there are out there ? I found this forum post.
Smart Host - Exim Cpanel - SMTP external outgoing mail server

I'd like some more clarity on the high level overview, would a simple postfix server with IP auth be acceptable to send mail on behalf of approx 200 domains ?

Also wondering if setting the MX records to the GCP instance is ok once the smart host config is done ?

Lastly does this set up have any issue with SSL certs and or mail headers and spf / dkim / anti spam when sending to sensitive recipients in Outlook etc etc.

Many thanks if you can join in with this discussion.

Kind Regards

Matt

#1

[Faizan (Google Cloud Support)]

Hello Matt,

I would recommend posting this question on stack overflow or server-fault. By doing so you will get access to bigger audience and better chance of getting answer to your questions. This forum is for discussions related to GCE and not a best place to look for 1:1 support.

I hope that helps.

Faizan

[Greg Piper]

Google Compute Engine has all standard outgoing SMTP ports blocked by design. Please vote here to get Google's SMTP behavior changed:
https://googlecloudplatform.uservoice.com/forums/302595-compute-engine/suggestions/10079937-send-and-receive-email-using-tcp-smtp-imap-ports

Until they open the SMTP ports, there will be no good way to send email from their cloud servers. Sendgrid and the others are too expensive and lack many features that are needed.