# 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:** 4

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### Author: ![tobiaseigen](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/tobiaseigen/32/539204_2.png) [@tobiaseigen](https://meta.discourse.org/u/tobiaseigen)
#### Post date: [November 12, 2025, 11:39pm UTC](https://meta.discourse.org/t/seeing-smtp-should-reject-400-bad-request-failures-on-bounce-processing/387431/4 "2025-11-12T23:39:18Z")

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What about your outbound email provider? Are you using mailgun or some other transactional email provider?

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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)._