As the title implies, we're looking for an inhouse SMTP server to use for all our server applications that have Email Alert features (i.e. WhatsUp Gold, our Windows Storage Server reports, etc, etc). MOST of the program we use allow for basic authentication to an SMTP server. Other programs don't even allow the use of a user name (just a mail server address and that's it!). Our company mail servers (hosted exchange) require us to pay extra for SMTP and only allow it if SSL is enabled, which 95% of the programs that we want to send out emails don't have an SSL option so they're out of the question.
I've tried setting up some sendmail and postfix servers here in house, but whenever I try to send mail, our Exchange server rejects it because it can't verify the hostname. I'm guessing it's doing an MX lookup on the sender address, which is just the hostname of the machine, so it's coming from something like "servername.localhost" which obviously doesn't exist.
I think the biggest hurdling block here is my lack of how mail servers work. Is this something that I'll need to have my mail provider fix? Is it something I can fix by making configuration changes in postfix/sendmail? What's the best way to get this internal mail server set up and working?