# Seeing smtp\_should\_reject "400 bad request" failures on bounce processing

**URL:** https://meta.discourse.org/t/seeing-smtp-should-reject-400-bad-request-failures-on-bounce-processing/387431
**Category:** Bug
**Tags:** mail-receiver
**Created:** [November 3, 2025, 7:48am UTC](https://meta.discourse.org/t/seeing-smtp-should-reject-400-bad-request-failures-on-bounce-processing/387431 "2025-11-03T07:48:47Z")
**Posts on this page:** 1
**Showing post:** 14

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### Author: ![supermathie](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/supermathie/32/507518_2.png) [@supermathie](https://meta.discourse.org/u/supermathie)
#### Post date: [November 13, 2025, 10:35pm UTC](https://meta.discourse.org/t/seeing-smtp-should-reject-400-bad-request-failures-on-bounce-processing/387431/14 "2025-11-13T22:35:40Z")

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Hi DevTeVe,

I’ve reviewed the code in question and I believe you are right - I think the `smtp_should_reject` code may be incorrectly rejecting bounce messages and replies.

I’m escalating this internally.

In the meanwhile, if you disable the `discourse-smtp-fast-rejection` policy filter does it allow mail to flow?

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_[View the full topic](https://meta.discourse.org/t/seeing-smtp-should-reject-400-bad-request-failures-on-bounce-processing/387431)._