550 No such local user processed as Soft Bounce

[Alpha1]

Affected version

2.3.10

These bounce messages should be hard bounces:

• 550 No such local user, unauthenticated relaying denied
• 550 Invalid Recipient

Same issue as this one, but with slightly different text:

Fixed Thread '550 permanent failure processed as Soft Bounce'

Nov 7, 2025

This bounce message is incorrectly processed as a Soft Bounce:

Action: failed
Final-Recipient: rfc822; xxx@evansinc.com
Diagnostic-Code: smtp; 550 permanent failure for one or more recipients (xxx@evansinc.com:550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EX...)
Status: 5.3.0

This clearly should be treated as a hard bounce.

• Alpha1
• bounce handling
• Replies: 4
• Forum: Resolved bug reports

 

[Alpha1]

Some more:

• smtp; 550 5.4.1 Recipient address rejected: Access denied
• smtp;550 5.1.10 RESOLVER.ADR.RecipientNotFound

The first one is a frequently occurring one by Microsoft.