[Dovecot] username and password not from /etc/passwd

Can dovecot use usernames and passwords not from /etc/passwd and be able to read mails of an user whose username and password are in /etc/passwd ?

For example: them in /var/mail/joe

• Joe Bloke has a local Unix account joe on Unix server mail.example.com
• Sendmail on mail.example.com accepts mails for joe@example.com and put

• can dovecot use other username/password file or database or directory rather than /etc/passwd to authenticate Joe and let him (once logs in successfully) reading mails in /var/mail/joe ? Ideally, the usernames and passwords that dovecot uses are different with the ones in /etc/passwd. Say, username is joe.bloke@example.com

That way, Joe doesn't need to know the username and password on the Unix server at all.

In summary, I want to have IMAP usernames and passwords totally different from the local Unix usernames and passwords. And users use only IMAP usernames and passwords to read their mails.

I use OpenBSD-3.4, Sendmail 8.12.9, dovecot-0.99.10p0 (pre-compiled packaged from OpenBSD).

Thanks, Zoong Pham