[Dovecot] dovecot-lda error

[Wesley M.]

Hi, 

I use Dovecot 2.0.13 on OpenBSD 5.0
When i try to send emails i
have the following error in /var/log/maillog 

Jan 5 11:23:49 mail50
postfix/pipe[29423]: D951842244C: to=, relay=dovecot, delay=0.02,
delays=0.01/0/0/0.01, dsn=5.3.0, status=bounced (command line usage error.
Command output: deliver: unknown option -- n Usage: dovecot-lda [-c ] [-a ]
[-d ] [-p ] [-f ] [-m ] [-e] [-k] )
Jan 5 11:23:49 mail50
postfix/qmgr[13787]: D951842244C: removed 

In my /etc/postfix/master.cf
:
# Dovecot LDA
dovecot unix - n n - - pipe
 flags=ODR
user=_dovecot:_dovecot argv=/usr/local/libexec/dovecot/deliver -f
${
sender} -d ${user}@${nexthop} -n -m ${extension}

How can i resolve that
?
Thank you very much for your replies.

Cheers, 

Wesley.