dovecot - Jan 2022 - LMTP error on trying to find passwd-file for Postfix recipient validation

Hello everyone,

I have following configurations (and more) at /etc/dovecot/local.conf in 
a "/VirtualUserFlatFilesPostfix/" setup :

[partial file content begins]

protocols = imap pop3 lmtp sieve

mail_location = maildir:~/data:INBOX=~/data/.INBOX

service lmtp {
 ??? unix_listener /var/spool/postfix/private/dovecot-lmtp {
 ??? ??? user = vmail
 ??? ??? group = vmail
 ??? ??? mode = 0660
 ??? }
}

protocol lmtp {
 ??? postmaster_address = postmaster at example.net
 ??? mail_plugins = $mail_plugins sieve
}

userdb {
 ??? driver = passwd-file
 ??? args = username_format=%u /srv/vmail/domains.d/%d/users.d/%n/etc/passwd
}

passdb {
 ?? ?driver = passwd-file
 ??? args = username_format=%u 
/srv/vmail/domains.d/%d/users.d/%n/etc/shadow.%Ls
}

service auth {
 ??? unix_listener /var/spool/postfix/private/auth {
 ??? ??? user = postfix
 ??? ??? group = postfix
 ??? ??? mode = 0660
 ??? }
}

[/partial file content ends]

Everyting works (IMAP mail is stored, IMAP/POP3 mail is retrieved, 
incoming SMTP mail from Postfix is delivered, Outgoing SMTP senders are 
authenticated from Postfix~SASL) BUT:

When incoming mail goes to a mailbox that does not exist, an error is 
logged by Dovecot, letter remains at Postfix queue, and no rejection 
message to sender (here host is /mail.example.net/):

[partial]$ cat /var/log/mail.log

2022-01-28T08:52:00.851751+01:00 correo postfix/smtpd[1853]: 
CFDA63A174B: client=mail.example.com[1.2.3.4]
2022-01-28T08:52:00.872248+01:00 correo postfix/cleanup[1881]: 
CFDA63A174B: message-id=<83c79ee1-6e2e-4e15-307e-17cdc7e2b814 at
example.com>
2022-01-28T08:52:00.884100+01:00 correo postfix/qmgr[1529]: CFDA63A174B: 
from=<johndoe at example.com>, size=854, nrcpt=1 (queue active)
2022-01-28T08:52:00.884507+01:00 correo postfix/smtpd[1853]: disconnect 
from mail.example.com[1.2.3.4] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 
quit=1 commands=7
2022-01-28T08:52:00.969275+01:00 correo postfix/lmtp[1882]: CFDA63A174B: 
to=<wronguser at example.net>, 
relay=mail.example.net[private/dovecot-lmtp], delay=0.43, 
delays=0.35/0.02/0.02/0.05, dsn=4.3.0, status=deferred (host 
mail.example.net[private/dovecot-lmtp] said: 451 4.3.0 
<wronguser at example.net> Temporary internal error (in reply to RCPT TO 
command))

[partial]$ cat /var/log/dovecot.log

2022-01-28 08:52:00 lmtp(1883): Info: Connect from local
2022-01-28 08:52:00 auth: Error: passwd-file(wronguser at example.net): 
stat(/srv/vmail/domains.d/example.net/users.d/wronguser/etc/passwd) 
failed: Address family not supported by protocol
2022-01-28 08:52:00 
lmtp(wronguser at example.net)<1883><xbrsNqCg82FbBwAAzZSvjA>: Error:
user
wronguser at example.net: Auth USER lookup failed
2022-01-28 08:52:00 lmtp(1883): Error: Failed to lookup user 
wronguser at example.net: Internal error occurred. Refer to server log for 
more information.
2022-01-28 08:52:00 lmtp(1883): Info: Disconnect from local: Client has 
quit the connection (state=READY)

Thank you for any help in debugging configuration or suggestion to 
enhance Postfix/Dovecot parameters.

Postfix 3.4

Dovecot 2.3

-- 

Narcis Garcia

__________
I'm using this dedicated address because personal addresses aren't
masked enough at this mail public archive. Public archive administrator should
fix this against automated addresses collectors.

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On Fri, 28 Jan 2022, Narcis Garcia wrote:
> Hello everyone,
>
> I have following configurations (and more) at /etc/dovecot/local.conf in a 
> "/VirtualUserFlatFilesPostfix/" setup :
>
> [partial file content begins]
[snip]
> When incoming mail goes to a mailbox that does not exist, an error is
logged
> by Dovecot, letter remains at Postfix queue, and no rejection message to 
> sender (here host is /mail.example.net/):
Wouldn't it make sense to prevent postfix from attempting to deliver (via
LMTP)
messages addressed to invalid users?

i.e. using virtual_mailbox_maps and/or virtual_alias_maps, as needed.
> [partial]$ cat /var/log/dovecot.log
>
> 2022-01-28 08:52:00 lmtp(1883): Info: Connect from local
> 2022-01-28 08:52:00 auth: Error: passwd-file(wronguser at example.net): 
> stat(/srv/vmail/domains.d/example.net/users.d/wronguser/etc/passwd) failed:
> Address family not supported by protocol
^^^ weird message, but maybe it's dovecot's way of saying "file not
found" :)

Good luck.