Enhanced status code Temporary

SMTP error X.4.6

Routing loop detected

Updated Jul 1, 2026

The short answer

Routing loop detected Common cause: Mail keeps forwarding between servers

Quick fix

Fix forwarding, MX, or routing configuration

4 - Temporary. Safe to retry. The message is not lost and most servers retry automatically.
This code is written X.4.6 because the reason is the same whether the failure is temporary (a 4 first digit) or permanent (a 5). Read the first digit of your own bounce to know which applies.

How to fix it

Fix forwarding, MX, or routing configuration

Related codes

X.4.0 Other or undefined network / routing status X.4.1 No answer from host X.4.2 Bad connection X.4.3 Directory server failure X.4.4 Unable to route X.4.5 Mail system congestion
All SMTP error codes
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