Solution “SMTPUTF8 is required, but was not offered by host”

Once on one mail server I noticed a message delivery error:

Undelivered Mail Returned to Sender
SMTPUTF8 is required, but was not offered by host

In my case, the error occurred due to the fact that a mail server that accepted a letter of a very old version and does not support SMTPUTF8, by default SMTPUTF8 is enabled in newer Postfix versions (> 3.0). As defined in RFC 6531 (SMTPUTF8 extension), RFC 6532 (Internationalized email headers), RFC 6533 (Internationalized delivery status notifications).

Let’s see the current Postfix version:

postconf mail_version
postconf -d | grep mail_version

You can disable SMTPUTF8 by specifying in the /etc/postfix/ file:

smtputf8_enable = no

To apply the changes, run the command:

postfix reload

If the smtputf8_enable option is not present in the /etc/postfix/ configuration file and Postfix is newer than 3.0, then SMTPUTF8 is enabled by default. Personally, I have SMTPUTF8 enabled on mail servers.

Also if the error occurs on the local server, for example:
SMTPUTF8 is required, but was not offered by host
then this may mean that for example SMTPUTF8 is enabled in Postfix but disabled in Amavis.

See my other articles about the mail server

Leave a comment

Leave a Reply