special "what's my ip" pop account

[A. Schulze]

Hello,

I like to enable the allow_nets Feature  
(http://wiki2.dovecot.org/PasswordDatabase/ExtraFields/AllowNets)
for my customers. To help them knowing there own IP I imagine a  
special mailbox/loginuser at the pop3 server.

That user could give a valid pop3 answer from a dummy pop3 server or
simply throw a login error with customised answer containing the IP  
information.

Has anybody done something similar or ideas to build such a system?

Thanks for ideas
Andreas