issue with email delivery going through Cloudron mailing lists.

[avatar1024]

@jdaviescoates Well, this is what I do for distribution list and it seems to work fine with Gmail addresses. But I have to say it isn't really a replacement for Cloudron lists. I find the current email situation really quite tricky on Cloudron, given:

1. issues with delivery on forwards to some providers like Gmail
2. issues with delivery when using an external SMTP (likely related to point 1) when trying to overcome bad IP rep (which with MS domains is a recurring issue with MS stupid IP range bans).

For work I have to now consider moving all our mailboxes out of Cloudron...which I would really want to avoid because of:

1. faff
2. because I love Cloudron and wanna promote it (but my users are getting pissed because of email problems).

@staff if you don;t really want to focus of changing the mailing function on Cloudron for now (and I totally respect and understand that this may not be your priority), can you advise on a working solution to use a address@domain.coop (with domain.coop being the Cloudron domain) which can be use as a list, where:

1. some mailboxes on this domain being hosted on Cloudron (so the MX has to remain pointing to the Cloudron server)
2. and while using an external SMTP server to ensure reliable email delivery

[d19dotca]

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?