I was using ChatGPT for some assistance on this, as I'm still struggling with this issue off-and-on-again, and it recommended applying this to the Haraka configuration:
[outbound.limits]
gmail.com=1/30s
Essentially rate limiting delivery to Gmail which should lessen the likelihood of being rate limited by Gmail. Is there a way for us to configure this at all for testing purposes? I can't seem to create the outbound.limits file due to the read-only file system in the mail container, so I'm not sure how I can try this.
Interestingly though, I noticed today that this issue only seems to happen if sending from a hotmail.com / outlook.com address to the hosted Cloudron domain name which then forwards to the gmail.com address will this issue be triggered. If I send to the same distribution list from my other email addresses, it seems to not trigger the rate limiting response. So it seems possibly related to the sending domain originally before the hosted domain itself, which Gmail occasionally seems to have problems with.
Since the error is also sometimes Gmail has detected this message exceeded its quota for sending 4.7.28 messages with the same Message-ID, is there any possibility that Cloudron's mailing list feature could rotate the message-ID to avoid Gmail flagging it?
