Enhanced status code

SMTP error X.6.8

UTF-8 reply required but not permitted

Updated Jul 1, 2026

The short answer

UTF-8 reply required but not permitted Common cause: Server needs SMTPUTF8 response support the client lacks

Quick fix

Use an SMTPUTF8-capable client

This code is written X.6.8 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

Use an SMTPUTF8-capable client

Related codes

X.6.0 Other or undefined media error X.6.1 Media not supported X.6.2 Conversion required and prohibited X.6.3 Conversion required but unsupported X.6.4 Conversion with loss performed X.6.5 Conversion failed
All SMTP error codes
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