[Dovecot] Mapping username only for auth

[Andy Cravens]

I am running Dovecot alpha 3 with authentication from the local shadow 
file.  I'd like to change the authentication to use our  radius server.  
I can probably do this through pam.

The usernames on the mail server are set up as first initial + last name 
( jdoe for John Doe ).  The usernames on the radius server are the 
employee number.  Is there a way to map the username to the employee 
number in dovecot before handing off the authentication to the radius 
server?  I want the usernames on the mail server to remain first initial 
+ last name.  I don't mind maintaining a mapping file to go from 
username to employee number because I can automate this task.

Has anybody done this?