Enhanced status code

SMTP error X.1.10

Recipient address has null MX

Updated Jul 1, 2026

The short answer

Recipient address has null MX Common cause: Recipient domain explicitly does not accept email

Quick fix

Do not retry unless the recipient domain changes its mail configuration

This code is written X.1.10 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

Do not retry unless the recipient domain changes its mail configuration

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
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Most rejections come back to sender reputation.

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