Enhanced status code Temporary

SMTP error X.4.3

Directory server failure

Updated Jul 1, 2026

The short answer

Directory server failure Common cause: DNS or another directory service was unavailable

Quick fix

Retry after DNS / directory service recovers

4 - Temporary. Safe to retry. The message is not lost and most servers retry automatically.
This code is written X.4.3 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

Retry after DNS / directory service recovers

Related codes

X.4.0 Other or undefined network / routing status X.4.1 No answer from host X.4.2 Bad connection X.4.4 Unable to route X.4.5 Mail system congestion X.4.6 Routing loop detected
All SMTP error codes
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