[Dovecot] user unknown with deliver

[Nikolay Shopik]

I'm getting user unknown when trying to deliver to Sent folder messages. 
   My master.cf part is:
copy2sent   unix  -       n       n       -       -       pipe
   flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/deliver -d 
${sasl_username} -m Sent

But it still won't work. I'm running 1.0.15

pluto postfix/pipe[30934]: 7470890C4DA: to=<bcc at bcc.example.com>, 
relay=copy2sent, delay=0.03, delays=0.02/0/0/0.01, dsn=5.1.1, 
status=bounced (user unknown)