address extension and .forwarding

[David Erickson [Permanent Link]]

I am interested in setting up Postfix for a user such that all email 
received by this user such that it is only delivered locally if the 
address has one specific extension, all other email to this user is 
forwarded to another email address (including any specified address 
extensions).
In a nutshell:
user+specificextension AT domain DOT com -> delivered locally
user+any_other_extension AT domain DOT com ->forwarded elsewhere
user AT domain DOT com ->forwarded elsewhere

Is this possible?

Thanks,
David