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

On 16/01/2026 17:48, Christophe Lohr via dovecot wrote:

Le 16/01/2026 `a 17:22, John Fawcett via dovecot a ecrit :

  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?

Yes, Bob and Alice are configured on Dovecot and can connect to it.
(Tested with Thunderbird.)
According to the log file, Dovecot accepts connections from
bob@my_domain.org and alice@my_domain.org

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Hi

where are the dovecot users configured? Maybe it would help if you post your configuration (doveconf -n).

John

Le 16/01/2026 à 21:17, Christophe Lohr via dovecot a écrit :

Le 16/01/2026 à 20:50, John Fawcett via dovecot a écrit :

...

where are the dovecot users configured?

in  /etc/dovecot/passwd

...

Maybe it would help if you post your configuration (doveconf -n).

Thankyou for your help. See attached file

hum, I think the mailing list removed the attached file... well, here is the content:

2.4.1-4 (7d8c0e5759): /etc/dovecot/dovecot.conf

Pigeonhole version 2.4.1-4 (0a86619f)

OS: Linux 6.12.63+deb13-amd64 x86_64 Debian 13.3

Hostname: pc-serveur

4 default setting changes since version 2.4.0

dovecot_config_version = 2.4.0 auth_allow_cleartext = yes auth_debug = yes auth_debug_passwords = yes auth_mechanisms = plain login auth_verbose = yes auth_verbose_passwords = yes default_login_user = vmail dovecot_storage_version = 2.4.0 first_valid_gid = 2222 first_valid_uid = 2222 fts_autoindex = yes fts_autoindex_max_recent_msgs = 999 fts_search_add_missing = yes info_log_path = /var/log/dovecot-info.log log_path = /var/log/dovecot.log mail_access_groups = vmail mail_driver = maildir mail_home = /var/spool/vmail/%{user} mail_inbox_path = /var/spool/vmail/%{user}/Maildir mail_path = ~/Maildir mail_privileged_group = mail protocols = imap lmtp ssl = no verbose_proctitle = yes namespace inbox { inbox = yes mailbox Drafts { auto = subscribe special_use = "\\Drafts" } mailbox Junk { auto = subscribe special_use = "\\Junk" } mailbox Trash { auto = subscribe special_use = "\\Trash" } mailbox Sent { auto = subscribe special_use = "\\Sent" } mailbox "Sent Messages" { special_use = "\\Sent" } } service imap-login { process_min_avail = 1 user = vmail inet_listener imap { port = 143 listen = 192.168.100.1 127.0.0.1 [::1] } inet_listener imaps { } } service pop3-login { inet_listener pop3 { } inet_listener pop3s { } } service submission-login { inet_listener submission { } inet_listener submissions { } } service lmtp { user = dovecot unix_listener lmtp { } unix_listener /var/spool/postfix/private/dovecot-lmtp { group = postfix mode = 0600 user = postfix } } service imap { } service pop3 { } service submission { } service auth { user = dovecot unix_listener auth-userdb { } unix_listener auth-chasquid-userdb { mode = 0660 user = chasquid } unix_listener auth-chasquid-client { mode = 0660 user = chasquid } unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } } service auth-worker { user = dovecot } service dict { unix_listener dict { } } ssl_server { cert_file = /etc/dovecot/private/dovecot.pem key_file = /etc/dovecot/private/dovecot.key } protocol lmtp { auth_username_format = %{user | username | lower} } passdb passwd-file { passwd_file_path = /etc/dovecot/passwd } userdb passwd-file { passwd_file_path = /etc/dovecot/passwd fields { gid = vmail home = /var/spool/vmail/%{user} uid = vmail } }

Le 16/01/2026 `a 21:17, Christophe Lohr via dovecot a ecrit :

 Le 16/01/2026 `a 20:50, John Fawcett via dovecot a ecrit :

   where are the dovecot users configured?

 in  /etc/dovecot/passwd

   Maybe it would help if you post your configuration (doveconf -n).

 Thankyou for your help. See attached file

hum, I think the mailing list removed the attached file... well, here is the content:

2.4.1-4 (7d8c0e5759): /etc/dovecot/dovecot.conf

Pigeonhole version 2.4.1-4 (0a86619f)

OS: Linux 6.12.63+deb13-amd64 x86_64 Debian 13.3

Hostname: pc-serveur

4 default setting changes since version 2.4.0

dovecot_config_version = 2.4.0 auth_allow_cleartext = yes auth_debug = yes auth_debug_passwords = yes auth_mechanisms = plain login auth_verbose = yes auth_verbose_passwords = yes default_login_user = vmail dovecot_storage_version = 2.4.0 first_valid_gid = 2222 first_valid_uid = 2222 fts_autoindex = yes fts_autoindex_max_recent_msgs = 999 fts_search_add_missing = yes info_log_path = /var/log/dovecot-info.log log_path = /var/log/dovecot.log mail_access_groups = vmail mail_driver = maildir mail_home = /var/spool/vmail/%{user} mail_inbox_path = /var/spool/vmail/%{user}/Maildir mail_path = ~/Maildir mail_privileged_group = mail protocols = imap lmtp ssl = no verbose_proctitle = yes namespace inbox { inbox = yes mailbox Drafts { auto = subscribe special_use = "\\Drafts" } mailbox Junk { auto = subscribe special_use = "\\Junk" } mailbox Trash { auto = subscribe special_use = "\\Trash" } mailbox Sent { auto = subscribe special_use = "\\Sent" } mailbox "Sent Messages" { special_use = "\\Sent" } } service imap-login { process_min_avail = 1 user = vmail inet_listener imap { port = 143 listen = 192.168.100.1 127.0.0.1 [::1] } inet_listener imaps { } } service pop3-login { inet_listener pop3 { } inet_listener pop3s { } } service submission-login { inet_listener submission { } inet_listener submissions { } } service lmtp { user = dovecot unix_listener lmtp { } unix_listener /var/spool/postfix/private/dovecot-lmtp { group = postfix mode = 0600 user = postfix } } service imap { } service pop3 { } service submission { } service auth { user = dovecot unix_listener auth-userdb { } unix_listener auth-chasquid-userdb { mode = 0660 user = chasquid } unix_listener auth-chasquid-client { mode = 0660 user = chasquid } unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } } service auth-worker { user = dovecot } service dict { unix_listener dict { } } ssl_server { cert_file = /etc/dovecot/private/dovecot.pem key_file = /etc/dovecot/private/dovecot.key } protocol lmtp { auth_username_format = %{user | username | lower} } passdb passwd-file { passwd_file_path = /etc/dovecot/passwd } userdb passwd-file { passwd_file_path = /etc/dovecot/passwd fields { gid = vmail home = /var/spool/vmail/%{user} uid = vmail } }

Hello,

I'm currently testing a new setup for my internal mail server with a similar configuration (I'm authenticating users against a Samba4 AD-DC) and I encountered the same error. I was starting to get desperate trying to troubleshoot it.

Am 16.01.2026 um 21:56 schrieb John Fawcett via dovecot:

Maybe this should be

protocol lmtp { auth_username_format = %{user | lower} }

That was the solution! Sometimes it's so simple when you think about it calmly and know where to look.

Thanks, John. You're my hero. And thanks, Christophe, for asking at just the right time. 😉

Best regards, Mike

On 19/01/2026 10:02 EET Christophe Lohr via dovecot <dovecot@dovecot.org> wrote:

Le 16/01/2026 à 21:56, John Fawcett via dovecot a écrit :

...

Maybe this should be

protocol lmtp { auth_username_format = %{user | lower} }

Great, thankyouverymuch! Authenticationseemstobeworkingfinenow.

Thingsareprogressingwell... but... Istillhaveoneproblem: thereisnodelivery.

WhichdirectionshouldIlook?

postqueue -p -Queue ID-  --Size-- ----Arrival Time---- -Sender/Recipient------- 7496C880028    7846 Mon Jan 19 08:48:06 bob7@my_domain.org (lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while sending end of data -- message may be sent more than once) alice7@my_domain.org

1F8D38800E7    7846 Mon Jan 19 08:21:42 bob7@my_domain.org (lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while sending end of data -- message may be sent more than once) alice7@my_domain.org

-- 15 Kbytes in 2 Requests.

Postfix logs:

2026-01-19T08:48:06.446455+01:00 pc-serveur postfix/smtpd[2476]: connect from linux7.my_domain.org[192.168.100.17] 2026-01-19T08:48:06.477701+01:00 pc-serveur postfix/smtpd[2476]: 7496C880028: client=linux7.my_domain.org[192.168.100.17], sasl_method=PLAIN, sasl_username=bob7@my_domain.org 2026-01-19T08:48:06.482176+01:00 pc-serveur postfix/cleanup[2480]: 7496C880028: message-id=<89c5190c-0cf6-4d9d-86d9-bd92070cfa87@my_domain.org> 2026-01-19T08:48:06.483278+01:00 pc-serveur postfix/qmgr[1721]: 7496C880028: from=<bob7@my_domain.org>, size=7846, nrcpt=1 (queue active) 2026-01-19T08:48:06.510492+01:00 pc-serveur postfix/lmtp[2481]: 7496C880028: to=<alice7@my_domain.org>, relay=pc-serveur.my_domain.org[private/dovecot-lmtp], delay=0.04, delays=0.02/0.01/0.01/0, dsn=4.4.2, status=deferred (lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while sending end of data -- message may be sent more than once) 2026-01-19T08:48:11.487184+01:00 pc-serveur postfix/smtpd[2476]: disconnect from linux7.my_domain.org[192.168.100.17] ehlo=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=6

Dovecot logs:

Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: Server accepted connection (fd=22) Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: auth client connected (pid=0) Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: client in: AUTH    1    PLAIN    service=smtp    nologin lip=192.168.100.1    rip=192.168.100.17 resp=AGJvYjdAdHAtcmVzZWF1eC5lbnN0Yi5vcmcAYm9iN3NlY3JldA== (previous base64 data may contain sensitive data) Jan 19 08:48:06 auth(bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: passwd-file: Performing passdb lookup Jan 19 08:48:06 auth(bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: passwd-file: lookup: user=bob7@my_domain.org file=/etc/dovecot/passwd Jan 19 08:48:06 auth(bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: passwd-file: Finished passdb lookup Jan 19 08:48:06 auth(bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: Auth request finished Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: client passdb out: OK    1 user=bob7@my_domain.org Jan 19 08:48:06 lmtp(2482): Info: Connect from local Jan 19 08:48:06 auth: Debug: conn unix:/run/dovecot/auth-userdb (pid=2482,uid=118): Server accepted connection (fd=24) Jan 19 08:48:06 auth: Debug: master in: USER    1 alice7@my_domain.org  protocol=lmtp Jan 19 08:48:06 auth(alice7@my_domain.org): Debug: passwd-file: Performing userdb lookup Jan 19 08:48:06 auth(alice7@my_domain.org): Debug: passwd-file: lookup: user=alice7@my_domain.org file=/etc/dovecot/passwd Jan 19 08:48:06 auth(alice7@my_domain.org): Debug: passwd-file: Finished userdb lookup Jan 19 08:48:06 auth: Debug: userdb out: USER    1 alice7@my_domain.org  uid=2222    gid=2222 home=/var/spool/vmail/alice7@my_domain.org Jan 19 08:48:06 auth: Debug: conn unix:/run/dovecot/auth-userdb (pid=2482,uid=118): auth-master client: Disconnected: Connection closed (fd=24) (created 2 msecs ago, handshake 2 msecs ago) Jan 19 08:49:51 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: Disconnected: Connection closed (fd=22)

Many thanks ! Regards, Christophe

Le 16/01/2026 `a 21:56, John Fawcett via dovecot a ecrit :

 Maybe this should be

 protocol lmtp {
      auth_username_format = %{user | lower}
    }

Great, thank you very much! Authentication seems to be working fine now. Things are progressing well... but... I still have one problem: there is no delivery.

Which direction should I look?

postqueue -p -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- 7496C880028 7846 Mon Jan 19 08:48:06 [1]bob7@my_domain.org (lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while sending end of data -- message may be sent more than once) [2]alice7@my_domain.org

1F8D38800E7 7846 Mon Jan 19 08:21:42 [3]bob7@my_domain.org (lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while sending end of data -- message may be sent more than once) [4]alice7@my_domain.org

-- 15 Kbytes in 2 Requests.

Postfix logs:

2026-01-19T08:48:06.446455+01:00 pc-serveur postfix/smtpd[2476]: connect from linux7.my_domain.org[192.168.100.17] 2026-01-19T08:48:06.477701+01:00 pc-serveur postfix/smtpd[2476]: 7496C880028: client=linux7.my_domain.org[192.168.100.17], sasl_method=PLAIN, [5]sasl_username=bob7@my_domain.org 2026-01-19T08:48:06.482176+01:00 pc-serveur postfix/cleanup[2480]: 7496C880028: message-id=[6]<89c5190c-0cf6-4d9d-86d9-bd92070cfa87@my_domain.org> 2026-01-19T08:48:06.483278+01:00 pc-serveur postfix/qmgr[1721]: 7496C880028: from=[7]<bob7@my_domain.org>, size=7846, nrcpt=1 (queue active) 2026-01-19T08:48:06.510492+01:00 pc-serveur postfix/lmtp[2481]: 7496C880028: to=[8]<alice7@my_domain.org>, relay=pc-serveur.my_domain.org[private/dovecot-lmtp], delay=0.04, delays=0.02/0.01/0.01/0, dsn=4.4.2, status=deferred (lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while sending end of data -- message may be sent more than once) 2026-01-19T08:48:11.487184+01:00 pc-serveur postfix/smtpd[2476]: disconnect from linux7.my_domain.org[192.168.100.17] ehlo=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=6

Dovecot logs:

Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: Server accepted connection (fd=22) Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: auth client connected (pid=0) Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: client in: AUTH 1 PLAIN service=smtp nologin lip=192.168.100.1 rip=192.168.100.17 resp=AGJvYjdAdHAtcmVzZWF1eC5lbnN0Yi5vcmcAYm9iN3NlY3JldA== (previous base64 data may contain sensitive data) Jan 19 08:48:06 auth([9]bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: passwd-file: Performing passdb lookup Jan 19 08:48:06 auth([10]bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: passwd-file: lookup: [11]user=bob7@my_domain.org file=/etc/dovecot/passwd Jan 19 08:48:06 auth([12]bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: passwd-file: Finished passdb lookup Jan 19 08:48:06 auth([13]bob7@my_domain.org,192.168.100.17,sasl:plain): Debug: Auth request finished Jan 19 08:48:06 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: client passdb out: OK 1 [14]user=bob7@my_domain.org Jan 19 08:48:06 lmtp(2482): Info: Connect from local Jan 19 08:48:06 auth: Debug: conn unix:/run/dovecot/auth-userdb (pid=2482,uid=118): Server accepted connection (fd=24) Jan 19 08:48:06 auth: Debug: master in: USER 1 [15]alice7@my_domain.org protocol=lmtp Jan 19 08:48:06 auth([16]alice7@my_domain.org): Debug: passwd-file: Performing userdb lookup Jan 19 08:48:06 auth([17]alice7@my_domain.org): Debug: passwd-file: lookup: [18]user=alice7@my_domain.org file=/etc/dovecot/passwd Jan 19 08:48:06 auth([19]alice7@my_domain.org): Debug: passwd-file: Finished userdb lookup Jan 19 08:48:06 auth: Debug: userdb out: USER 1 [20]alice7@my_domain.org uid=2222 gid=2222 [21]home=/var/spool/vmail/alice7@my_domain.org Jan 19 08:48:06 auth: Debug: conn unix:/run/dovecot/auth-userdb (pid=2482,uid=118): auth-master client: Disconnected: Connection closed (fd=24) (created 2 msecs ago, handshake 2 msecs ago) Jan 19 08:49:51 auth: Debug: conn unix:auth (pid=2476,uid=122) [3]: Disconnected: Connection closed (fd=22)

Many thanks ! Regards, Christophe

Looks like the logs are missing all the useful things that would've hopefully come after this. The error is coming from lmtp, not auth.

Aki

On 19/01/2026 11:53 EET Christophe Lohr via dovecot <dovecot@dovecot.org> wrote:

Le 19/01/2026 à 09:07, Aki Tuomi via dovecot a écrit :

...

Looks like the logs are missing all the useful things that would've hopefully come after this. The error is coming from lmtp, not auth.

How can I ask Dovecot to produce more logs concerning lmtp?

From the postfix side I just have: "lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while receiving the initial server greeting" I'd like to know why...

Best regards Christophe Le 19/01/2026 `a 09:07, Aki Tuomi via dovecot a ecrit :

Looks like the logs are missing all the useful things that would've hopefully come after this. The error is coming from lmtp, not auth.

How can I ask Dovecot to produce more logs concerning lmtp?

From the postfix side I just have: "lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while receiving the initial server greeting" I'd like to know why...

Best regards Christophe

you can try

log_debug=category=lmtp

Aki

sorry without ssl enabled (typo)

Thanks - Paul Kudla (Manager SCOM.CA Internet Services Inc.)

Have A Happy Monday AND Happy Sucessful 2026 !

Scom.ca Internet Services <http://www.scom.ca> 104-1009 Byron Street South Whitby, Ontario - Canada L1N 4S3

Toronto 416.642.7266 Main 1.866.411.7266 Fax 1.888.892.7266 Email paul@scom.ca

On 2026-01-19 7:14 a.m., Paul Kudla via dovecot wrote:

ok these go in to dovecot config file

switch various debug = yes

also make sure debug log path = syslog so everything goes to the system logger

also best to try with ssl enabled first as that can cause complications until you are up and running.

auth_debug = no auth_debug_passwords = no

default_process_limit = 16384

mail_debug = no

#lock_method = dotlock #mail_max_lock_timeout = 300s

#mbox_read_locks = dotlock #mbox_write_locks = dotlock

mmap_disable = yes dotlock_use_excl = no mail_fsync = always mail_nfs_storage = no mail_nfs_index = no

#submission_host = 10.220.0.2:25

auth_mechanisms = plain login auth_verbose = yes base_dir = /data/dovecot/run/ debug_log_path = syslog disable_plaintext_auth = no dsync_features = empty-header-workaround

Thanks - Paul Kudla (Manager SCOM.CA Internet Services Inc.)

Have A Happy Monday AND Happy Sucessful 2026 !

Scom.ca Internet Services <http://www.scom.ca> 104-1009 Byron Street South Whitby, Ontario - Canada L1N 4S3

Toronto 416.642.7266 Main 1.866.411.7266 Fax 1.888.892.7266 Email paul@scom.ca

On 2026-01-19 4:58 a.m., Aki Tuomi via dovecot wrote:

...

...

On 19/01/2026 11:53 EET Christophe Lohr via dovecot <dovecot@dovecot.org> wrote:

Le 19/01/2026 à 09:07, Aki Tuomi via dovecot a écrit :

...

Looks like the logs are missing all the useful things that would've hopefully come after this. The error is coming from lmtp, not auth.

How can I ask Dovecot to produce more logs concerning lmtp?

  From the postfix side I just have: "lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while receiving the initial server greeting" I'd like to know why...

Best regards Christophe Le 19/01/2026 `a 09:07, Aki Tuomi via dovecot a ecrit :

  Looks like the logs are missing all the useful things that would've hopefully come after this. The error is coming from lmtp, not auth.

    How can I ask Dovecot to produce more logs concerning lmtp?

    From the postfix side I just have: "lost connection with pc-serveur.my_domain.org[private/dovecot-lmtp] while receiving the initial server greeting" I'd like to know why...

    Best regards Christophe

you can try

log_debug=category=lmtp

Aki

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Drop user=dovecot from service lmtp.

Aki

On 19/01/2026 14:35 EET Christophe Lohr via dovecot <dovecot@dovecot.org> wrote:

Le 19/01/2026 à 10:58, Aki Tuomi via dovecot a écrit :

...

you can try

log_debug=category=lmtp

Many thanks!

Thereisclearlysomeconfusionsomewherebetweenthevmailuserandthedovecotuser(nottomentionthatanvilisundertherootuser):

Jan 19 13:13:56 lmtp(4940): Error: conn unix:/run/dovecot/anvil: net_connect_unix(/run/dovecot/anvil) failed: Permission denied Jan 19 13:13:56 lmtp(alice7@my_domain.org)<4940><g39gDwQgbmlMEwAAfWgqOQ>: Fatal: setresgid(2222(vmail),2222(vmail),8(mail)) failed with euid=118(dovecot): Operation not permitted Jan 19 13:13:56 lmtp: Fatal: master: service(lmtp): child 4940 returned error 89 (Fatal failure)

How can I fix this?

Best regards Christophe

PS:  Here is my current doveconf:

2.4.1-4 (7d8c0e5759): /etc/dovecot/dovecot.conf

Pigeonhole version 2.4.1-4 (0a86619f)

OS: Linux 6.12.63+deb13-amd64 x86_64 Debian 13.3

Hostname: pc-serveur

4 default setting changes since version 2.4.0

dovecot_config_version = 2.4.0 auth_allow_cleartext = yes auth_debug = yes auth_debug_passwords = yes auth_mechanisms = plain auth_verbose = yes auth_verbose_passwords = yes default_login_user = vmail dovecot_storage_version = 2.4.0 first_valid_gid = 2222 first_valid_uid = 2222 fts_autoindex = yes fts_autoindex_max_recent_msgs = 999 fts_search_add_missing = yes info_log_path = /var/log/dovecot-info.log log_debug = category=lmtp log_path = /var/log/dovecot.log mail_access_groups = vmail mail_driver = maildir mail_home = /var/spool/vmail/%{user|lower} mail_inbox_path = /var/spool/vmail/%{user|lower}/Maildir mail_path = ~/Maildir mail_privileged_group = mail protocols = imap lmtp ssl = no verbose_proctitle = yes namespace inbox { inbox = yes mailbox Drafts { special_use = "\\Drafts" } mailbox Junk { special_use = "\\Junk" } mailbox Trash { special_use = "\\Trash" } mailbox Sent { special_use = "\\Sent" } mailbox "Sent Messages" { special_use = "\\Sent" } } service imap-login { process_min_avail = 1 user = vmail inet_listener imap { port = 143 listen = 192.168.100.1 127.0.0.1 [::1] } inet_listener imaps { } } service pop3-login { inet_listener pop3 { } inet_listener pop3s { } } service submission-login { inet_listener submission { } inet_listener submissions { } } service lmtp { executable = lmtp -L user = dovecot unix_listener lmtp { } unix_listener /var/spool/postfix/private/dovecot-lmtp { group = postfix mode = 0600 user = postfix } } service imap { } service pop3 { } service submission { } service auth { user = dovecot unix_listener auth-userdb { } unix_listener auth-chasquid-userdb { mode = 0660 user = chasquid } unix_listener auth-chasquid-client { mode = 0660 user = chasquid } unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } } service auth-worker { user = dovecot } service dict { unix_listener dict { } } ssl_server { cert_file = /etc/dovecot/private/dovecot.pem key_file = /etc/dovecot/private/dovecot.key } protocol lmtp { auth_username_format = %{user|lower} info_log_path = /var/log/dovecot-lmtp.log } passdb passwd-file { passwd_file_path = /etc/dovecot/passwd } userdb passwd-file { passwd_file_path = /etc/dovecot/passwd fields { gid = vmail home = /var/spool/vmail/%{user|lower} uid = vmail } } Le 19/01/2026 `a 10:58, Aki Tuomi via dovecot a ecrit :

you can try

log_debug=category=lmtp

Many thanks!

There is clearly some confusion somewhere between the vmail user and the dovecot user (not to mention that anvil is under the root user):

Jan 19 13:13:56 lmtp(4940): Error: conn unix:/run/dovecot/anvil: net_connect_unix(/run/dovecot/anvil) failed: Permission denied Jan 19 13:13:56 lmtp([1]alice7@my_domain.org)<4940><g39gDwQgbmlMEwAAfWgqOQ>: Fatal: setresgid(2222(vmail),2222(vmail),8(mail)) failed with euid=118(dovecot): Operation not permitted Jan 19 13:13:56 lmtp: Fatal: master: service(lmtp): child 4940 returned error 89 (Fatal failure)

How can I fix this?

Best regards Christophe

PS: Here is my current doveconf:

2.4.1-4 (7d8c0e5759): /etc/dovecot/dovecot.conf

Pigeonhole version 2.4.1-4 (0a86619f)

OS: Linux 6.12.63+deb13-amd64 x86_64 Debian 13.3

Hostname: pc-serveur

4 default setting changes since version 2.4.0

dovecot_config_version = 2.4.0 auth_allow_cleartext = yes auth_debug = yes auth_debug_passwords = yes auth_mechanisms = plain auth_verbose = yes auth_verbose_passwords = yes default_login_user = vmail dovecot_storage_version = 2.4.0 first_valid_gid = 2222 first_valid_uid = 2222 fts_autoindex = yes fts_autoindex_max_recent_msgs = 999 fts_search_add_missing = yes info_log_path = /var/log/dovecot-info.log log_debug = category=lmtp log_path = /var/log/dovecot.log mail_access_groups = vmail mail_driver = maildir mail_home = /var/spool/vmail/%{user|lower} mail_inbox_path = /var/spool/vmail/%{user|lower}/Maildir mail_path = ~/Maildir mail_privileged_group = mail protocols = imap lmtp ssl = no verbose_proctitle = yes namespace inbox { inbox = yes mailbox Drafts { special_use = "\\Drafts" } mailbox Junk { special_use = "\\Junk" } mailbox Trash { special_use = "\\Trash" } mailbox Sent { special_use = "\\Sent" } mailbox "Sent Messages" { special_use = "\\Sent" } } service imap-login { process_min_avail = 1 user = vmail inet_listener imap { port = 143 listen = 192.168.100.1 127.0.0.1 [::1] } inet_listener imaps { } } service pop3-login { inet_listener pop3 { } inet_listener pop3s { } } service submission-login { inet_listener submission { } inet_listener submissions { } } service lmtp { executable = lmtp -L user = dovecot unix_listener lmtp { } unix_listener /var/spool/postfix/private/dovecot-lmtp { group = postfix mode = 0600 user = postfix } } service imap { } service pop3 { } service submission { } service auth { user = dovecot unix_listener auth-userdb { } unix_listener auth-chasquid-userdb { mode = 0660 user = chasquid } unix_listener auth-chasquid-client { mode = 0660 user = chasquid } unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } } service auth-worker { user = dovecot } service dict { unix_listener dict { } } ssl_server { cert_file = /etc/dovecot/private/dovecot.pem key_file = /etc/dovecot/private/dovecot.key } protocol lmtp { auth_username_format = %{user|lower} info_log_path = /var/log/dovecot-lmtp.log } passdb passwd-file { passwd_file_path = /etc/dovecot/passwd } userdb passwd-file { passwd_file_path = /etc/dovecot/passwd fields { gid = vmail home = /var/spool/vmail/%{user|lower} uid = vmail } }

References

Visible links

1. mailto:alice7@my_domain.org

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note postfix has log levels set to 15 for everything.

Thanks - Paul Kudla (Manager SCOM.CA Internet Services Inc.)

Have A Happy Monday AND Happy Sucessful 2026 !

Scom.ca Internet Services <http://www.scom.ca> 104-1009 Byron Street South Whitby, Ontario - Canada L1N 4S3

Toronto 416.642.7266 Main 1.866.411.7266 Fax 1.888.892.7266 Email paul@scom.ca

On 2026-01-19 4:53 a.m., Christophe Lohr via dovecot wrote:

Le 19/01/2026 `a 09:07, Aki Tuomi via dovecot a ecrit :

Looks like the logs are missing all the useful things that would've hopefully come after this. The error is coming from lmtp, not auth.

How can I ask Dovecot to produce more logs concerning lmtp?

From the postfix side I just have: "lost connection with
pc-serveur.my_domain.org[private/dovecot-lmtp] while receiving the initial
server greeting"
I'd like to know why...

Best regards
Christophe

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