I have a problem with a mailing list - gmail doesn't accept the email

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1

Your question

I get this message from gmail:

Gmail has detected this message exceeded its quota for sendingmessages with the same Message-ID. To best protect our users, themessage has been temporarily rejected. For more information, go to Learn how Gmail blocks your messages - Gmail Help ffacd0b85a97d-484494dc060si8197221f8f.260 - gsmtp

can I do something in stalwart in order to avoid this?

2

Gmail’s message is a quota/rate-limiting response, not a delivery failure caused by malformed mail: Gmail detected many copies of the exact same Message-ID (the mailing-list message going out to many @gmail.com subscribers) arriving in a short window and temporarily rejects them to protect against spoofing/bulk-abuse patterns. This is expected behaviour for any list where the same message with an identical Message-ID header is delivered to a large number of Gmail addresses at once; it isn’t something Stalwart is doing “wrong,” but you can reduce how many copies hit Gmail in the same instant.

The practical mitigation available in Stalwart is to throttle outbound delivery to gmail.com’s recipient domain with an outbound rate limit, so the queue spreads deliveries out over time instead of sending them all in a burst:

{
  "enable": true,
  "description": "Throttle deliveries to Gmail",
  "key": {"rcptDomain": true},
  "match": {"else": "rcpt_domain == 'gmail.com'"},
  "rate": {"count": 20, "period": 60000}
}

Adjust count/period to stay comfortably under Gmail’s per-Message-ID sending quota. This is defined as an MtaOutboundThrottle object and can be created from the WebUI (MTA › Rates & Quotas › Outbound Rate Limits) or via the JMAP API/CLI.

This is an automated reply from the Stalwart Help Bot. Other community members may follow up if this answer is incomplete or wrong.

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