Adding another port to sendmail

["Ashley M. Kirchner" <ashley@xxxxxxxxxx>]

   How do I configure sendmail to listen (and use) another port, IN 
ADDITION to port 25?  Our outgoing mail server uses port 25 for internal 
stuff, and for our remote users using authentication, I'd like them to 
use port 2525 (specially since a few of them have port < 1024 blocked by 
their ISP.)  So I need to have sendmail be able to use both port 25 as 
well as 2525 (or whatever other port number, 2525 just seemed logical.)