Where is imapd.conf option to direct postfix to /var/spool/imapd/user/mailbox?

Sat Sep 17 13:21:43 EDT 2005

I am using postfix+cyrus+sasl+webcryadm. When logging to imap accounts the 
following complaint appears in maillog:

pop3: login: [192.168.2.154] benu0001 plaintext User logged in
pop3: IOERROR: opening /var/spool/imap/b/user/benu0001/cyrus.header: No such 
file or directory
pop3: Unable to open maildrop for benu0001: System I/O error

Pop is attempting to open the incorrect file /var/.../b/user/benu0001 when it 
should be just /var/.../user/benu0001. Which imap option is adding the /b/ to 
the mailbox file name?

thanks,
flashl