SMTP spoofing ?

Are there any routers currently available that can do port 25 spoofing for dialup users? That is, when the user attempts to connect to port 25 anywhere, he in fact connects to port 25 on your own SMTP server instead. In case it's not obvious, it's for spam management. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Information Superhighwayman wanna-be, http://iecc.com/johnl, Sewer Commissioner Finger for PGP key, f'print = 3A 5B D0 3F D9 A0 6A A4 2D AC 1E 9E A6 36 A3 47