dovecot - Apr 2012 - Dovecot Virtual Users with Users Domain Mapping

I have successfully compiled, configured and ran Dovecot with virtual users
feature.

Here's part of my /etc/dovecot.conf configuration file:
mail_location = maildir:~/Maildir

auth default {
mechanisms = plain login

userdb passwd-file {
args = /home/%d/etc/passwd
}

passdb passwd-file {
args = /home/%d/etc/shadow
}

socket listen {
master {
path = /var/run/dovecot/auth-worker
mode = 0600
}
}
}

I faced one issue I can't resolve myself. Is there anyway to create
users'
domains mapping and provide username in mail_location?
Example of usersdomains file:
domain.com:user1
domain2.org:user3

Examples: 1. currently I have /home/domain.com/user/Maildir 2. I'd like to
have /home/SYSTEM_USER/domain.com/user/Maildir

Can I achieve this somehow?