Enhanced status code

SMTP error X.1.6

Destination mailbox moved, no forwarding address

Updated Jul 1, 2026

The short answer

Destination mailbox moved, no forwarding address Common cause: Mailbox existed previously but no longer accepts mail

Quick fix

Get the recipient's current address

This code is written X.1.6 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

Get the recipient's current address

Related codes

X.1.0 Other address status X.1.1 Bad destination mailbox address X.1.2 Bad destination system address X.1.3 Bad destination mailbox address syntax X.1.4 Destination mailbox address ambiguous X.1.5 Destination address valid
All SMTP error codes
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