On 16/01/2026 15:09, Christophe Lohr via dovecot wrote:
Hello,
Please excuse my naive question.
I am trying to understand how "service auth" is supposed to work
between Postfix and Dovecot.
(https://doc.dovecot.org/2.4.2/howto/sasl/postfix.html)
Here is my test setup:
- dovecot and postfix talking in lmtpd (via unix_listener
/var/spool/postfix/private/dovecot-lmtp)
- dovecot and postfix talking in sasl (via unix_listener
/var/spool/postfix/private/auth)
- "bob" and "alice" are virtual users of the virtual domain
"my_domain.org"
- passwd-file (plain) is /etc/dovecot/passwd
Now, postrfix receive (by smtp) an email From: bob@my_domain.org To:
alice@my_domain.org
Postfix validate the domain according to its config (main.cf:
virtual_mailbox_domains=my_domain.org)
Then, it queries dovecot about these users via sasl: and that's where
it fails!
Here are logs from postfix:
2026-01-16T14:28:55.829532+01:00 pc-serveur postfix/qmgr[25055]:
CA20D880486: from=<bob@my_domain.org>, size=9988, nrcpt=1 (queue active)
2026-01-16T14:28:55.831365+01:00 pc-serveur postfix/lmtp[25080]:
CA20D880486: to=<alice@my_domain.org>,
relay=pc-serveur.my_domain.org[private/dovecot-lmtp], delay=0,
delays=0/0/0/0, dsn=5.1.1, status=bounced (host
pc-serveur.tp-reseaux.enstb.org[private/dovecot-lmtp] said: 550 5.1.1
<alice@my_domain.org> User doesn't exist: alice@my_domain.org (in
reply to RCPT TO command))
That does not look like a sasl request. This is postfix lmtp delivery
agent connecting to dovecot to deliver the message to dovecot, but
dovecot rejecting the email due to user not found.
Here are logs from dovecot:
Jan 16 14:28:55 lmtp(25081): Info: Connect from local
Jan 16 14:28:55 auth: Debug: conn unix:/run/dovecot/auth-userdb
(pid=25081,uid=118): Server accepted connection (fd=24)
Jan 16 14:28:55 auth: Debug: master in: USER 1 bob@my_domain.org
protocol=lmtp
Jan 16 14:28:55 auth(bob7): Debug: passwd-file: Performing userdb lookup
Jan 16 14:28:55 auth(bob7): Debug: passwd-file: lookup: user=bob7
file=/etc/dovecot/passwd
Jan 16 14:28:55 auth(bob7): Info: passwd-file: unknown user
Jan 16 14:28:55 auth(bob7): Debug: passwd-file: Finished userdb lookup
Jan 16 14:28:55 auth: Debug: userdb out: NOTFOUND 1
Jan 16 14:28:55 lmtp(25081): Info: Disconnect from local: Logged out
(state=READY)
Jan 16 14:28:55 lmtp(25081): Info: Connect from local
Jan 16 14:28:55 auth: Debug: master in: USER 2 alice@my_domain.org
protocol=lmtp
Jan 16 14:28:55 auth(alice7): Debug: passwd-file: Performing userdb
lookup
Jan 16 14:28:55 auth(alice7): Debug: passwd-file: lookup: user=alice7
file=/etc/dovecot/passwd
Jan 16 14:28:55 auth(alice7): Info: passwd-file: unknown user
Jan 16 14:28:55 auth(alice7): Debug: passwd-file: Finished userdb lookup
Jan 16 14:28:55 auth: Debug: userdb out: NOTFOUND 2
Jan 16 14:28:55 lmtp(25081): Info: Disconnect from local: Logged out
(state=READY)
So, what's wrong?
It seems to me that Dovecot receives a SASL request for the user
"bob@my_domain.org", but only does a lookup for "bob", without the
domain. Isn't it?
So, why? What can I do?
Best regards,
Christophe
Have you configured users on dovecot and are you able to login to imap
ok? Before integrating postfix and dovecot, is dovecot configured and
working?
John
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