My local SMTP relay is finding it increasingly difficult to deliver mail to my G-Suite groups and users. The volume is not very high, but Google enforces rather low limits on incoming e-mail from external sources. Something like 180 per 20 minutes and 360 per hour.
Due to the way Google count delivery attempts, it looks like I need to make sure retries after a temporary delivery error (450) are directed to the same server as the original attempt, and only after a certain backoff time has passed.
The default behavior appear to be an immediate attempt on one of the secondary MX servers before deferring for the configured backoff time. This causes Google to count yet another delivery attempt and adding to the time before a delivery will be accepted.
How might this be accomplished in postfix?
