On Sun, Oct 18, 2026 at 03:09:36PM +0200, Danjel Jungersen via Postfix-users 
wrote:

> The remote user did reply, but the incoming mail was not delivered.
> 
> 2026-10-12T18:40:50.760730+02:00 mail postfix/lmtp[116517]:
>   EFCA110E01DB: to=<[email protected]>,
>   relay=mail.jungersen.dk[private/dovecot-lmtp], delay=1.8,
>   delays=1.7/0.07/0.09/0, dsn=5.6.7, status=bounced
>   (SMTPUTF8 is required, but was not offered by host 
> mail.jungersen.dk[private/dovecot-lmtp])
> 
> As I read this, the remote serve requires utf8, but also uses the
> alternative utf8-free address.

Not the remote server, rather your Dovecot LMTP service listening on a
unix-domain socket.  You need to enable SMTPUTF8 support in the dovecot
LMTP service.

My friendly AI suggests:

  Historical Context vs. Modern Support

    Historically (Dovecot v2.3 and earlier):
      Dovecot did not support SMTPUTF8 in its LMTP implementation.
      Administrators integrating Postfix with Dovecot LMTP were
      routinely advised to set smtputf8_enable = no in Postfix to
      prevent delivery failures when emails contained non-ASCII
      characters or emojis.

    Modern Dovecot (v2.4+):
      Dovecot introduced experimental support for mail UTF-8 extensions,
      which brings SMTPUTF8 support to LMTP (alongside Submission and
      IMAP). 

    How to Enable It

    To use SMTPUTF8 with Dovecot LMTP, ensure the following requirements are 
met:

    1. Dovecot must be built with the `--enable-experimental-mail-utf8`
       configure flag (pre-built community packages often have this enabled
       by default).
    2. You must explicitly enable the setting in your Dovecot configuration:

         mail_utf8_extensions = yes

       Setting this option to `yes` enables SMTPUTF8 handling for LMTP and
       Submission sessions, and `UTF8=ACCEPT` for IMAP sessions.

-- 
    Viktor.  🇺🇦 Слава Україні!
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