>> Is there a ready made mail server object in NT5?
nope.
<< Instead of my app polling a POP3 server, I want my app to be the email server. It isn't going to relay mail, instead it is the destination.
>> Is it as simple as using a NetSimple object and listening on port 25 for the incoming email packet?
yes and no. Yes, that's what you'll do. but to be a mail server, even just a listening SMTP server is a lot of work. You have to handle pretty much the whole SMTP spec, and that's quite a lot.
We do obviously make the CapeSoft Email Server and in almost all circumstances it's gonna be preferable to use something like that.
Cheers
Bruce