[wlug] Sendmail + catchall account

Hi Is there any way of creating a 'catchall' or a default account that all undelivered mail can go to ? eg if we have 3 user accounts (user1, user2, admin) already set up, but someone sends an email to user3(a)mydomain.com, can sendmail figure out that it doesn't match any existing users and deliver it to admin(a)mydomain.com ? I am using sendmail-8.13.1-3.RHEL4.5 Best Regards N