no mailbox here by that name (chkuser) ?

Hello,
I'm managing an email server that recently started to refuse inbound mail to a 
few domains.

I checked almost everything and the declaration seems to be exactly the same for 
others domains.

For example :
<[email protected]>:
195.200.217.34 does not like recipient.
Remote host said: 550 5.1.1 sorry, no mailbox here by that name (chkuser)
Giving up on 195.200.217.34.

Every address for this domain is refused (even aliases).

# vadduser -v
version: 5.4.17

vpopmail + mysql.

No mysql connection error.
Declaration in /var/qmail/control/(rcpthosts|virtualdomains|users/assign) is the 
same as other domains that works.

User is declared in the vpopmail mysql database.

I destroyed the domain and recreate it on the shell and in qmailadmin without 
success.

User can authenticate in the webmail (squirrelmail, IMAP, dovecot).

I googled a few hours on this subject without finding a clue.

What else may I check ?

Thans for your help,
Julien Escario

!DSPAM:4c88ade732716941516972!