Microsoft bounces: Why you receive both thread.replied and message.bounce_detected

When an email bounces on a Microsoft connection, you may receive two webhook notifications for the same event:

  1. message.bounce_detected
  2. thread.replied

This happens because Microsoft Exchange delivers bounce notifications (NDRs) as a new message in the same conversation thread as the original email. Nylas correctly identifies it as both a bounce and a thread reply — so both webhooks fire.

On Google, bounces arrive as separate messages outside the thread, so you only get message.bounce_detected.

Providermessage.bounce_detectedthread.replied
Google
Microsoft

Want this changed?

If you'd like Nylas to suppress the thread.replied webhook for bounces, please submit a feature request.

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