Some users without local mail delivery (postfix/smtpd: NOQUEUE: reject: RCPT from localhost[127.0.0.1]: 550 5.1.1 <auser@ynh.example.com>: Recipient address rejected: User unknown in virtual mailbox table

We’re running YunoHost 11.1.2 (testing). Our server (rewrited) at ynh.example.com

In postfix logs, I get errors like:

ynh postfix/smtpd: NOQUEUE: reject: RCPT from localhost[127.0.0.1]: 550 5.1.1 <auser@ynh.example.com>: Recipient address rejected: User unknown in virtual mailbox table

The users are in LDAP, and have access to apps on ynh.example.com.

Dovecot is installed, but these users haven’t (yet ?) logged in to the Webmail (or through IMAP).

Hence, no /var/spool/mail/auser (either dir or file)

Other users however do receive mail into their Dovecot box (under /var/spool/mail/anotheruser/ dir). Example log then (user is an admin):

ynh dovecot: lda(anotheruser@ynh.example.com)<XXXXX><XXXXXX>: sieve: msgid=<XXXXXX@ynh.example.com>: stored mail 
into mailbox 'INBOX'
ynh postfix/pipe: XXXXXX: to=<anotheruser@ynh.example.com>, orig_to=<root@ynh.example.com>, relay=dovecot, delay=4.2, delays=0.01/4/0/0.1
4, dsn=2.0.0, status=sent (delivered via dovecot service)

I suspect some kind of misconfiguration in the LDAP properties or another thing that makes postfix recognize the user as a local user whose delivery must be passed to dovecot…

I have probably some users working as having been created before and others not, after an upgrade of some of the packages…

Any hints ?

Thanks in advance.