Webserver Magically Sending emails through to local exchange

Question

I have recently inherited an IT setup for a company done by a guy who went AWOL and I have had to try and figure out what is going on.

Recently, the company has moved premises and I have had to set everything up - I almost got it all going except for an issue with emails not coming through.

The setup is that an external unix-based webserver "magically" catches the emails and forwards them on through. The exchange server that sits on the premises and gets the emails some how.

I know the webserver has an "MX Entry" that contains mail.domain.com and a DNS Zone File Record for mail.domain.com which points to the external IP for the router.

That static IP set up by the ISP has not changed due to the move (they have kept the same one)

At this point my best guess is that there is something I need to do to the router so that it knows that when it allows mail.domain.com through to the local exchange sever. I don't even know where to start looking, and I have a dinky little fritz-box router which is very shiney but doesn't let me do much out of the ordinary.

I am also able to remote-desktop into it by using mail.domain.com as well so I am sure there is some magical routing rule that I am missing that allows all this.

If something could point me in the right direction that would be great.

Answer 1

Is this a new router or was it moved as well?

If it is the same router, it ought to be working. Otherwise, it sounds like the web server is also a DNS server with an MX record pointing to your perimeter router/firewall. All you need to do here is forward TCP/25 to the internal IP of your anti-spam box or directly to your Exchange server if you aren't using a dedicated appliance for message filtering. You will also need a firewall rule to allow the traffic in addition to the NAT mentioned above.