Notification E-mails

[Qmail-User]

Say if a user has 2 or 3 mail accounts and only one is the primary account
that he checks every day.  Is it possible to get qmail to send the user
notification of new e-mails when they arrive in his other 2 accounts?  I
assume some command would have to go into the .qmail file in the home
directories of his other 2 accounts but what commands?

Regards

Vivian Lal