I self-host a number of Discourse instances using mail-receiver. I noticed the conversation below, and am wondering – do I need to Rebuild the mail-receiver.yml files for these sites?
Continuing the discussion from Seeing smtp_should_reject "400 bad request" failures on bounce processing :
I’m making this topic to summarise some internal discussion we’ve had.
We’ve identified that the codepath in smtp_should_reject is not functioning correctly and causing mail to be rejected in situations where it should not be.
Specifically:
bounce messages (having a null envelope-from)
forwarded mail to mismatch (the fast-rejection check used the envelope-to, whereas Discourse uses the…
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supermathie
November 25, 2025, 8:42pm
2
You can update either mail-receiver or Discourse and it’ll fix the problem.
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