I spent half of Friday, all of Monday and the first part of Tuesday attacking the office firewall with a hammer… ok, not really. But it was coming close to that. I kept fiddling with all the configurations to try to get incoming SMTP working but to no avail. What was confusing was that attempts to connect to port 25 were appearing in the firewall logs but the connection would ultimately fail.

Eventually a light bulb went on over my head and I realised that it must be my ISP blocking it. So I rang them up and asked them… and they were! I asked them to open the port up on the IP our Exchange server uses and they did it within the hour.

Everything now works perfectly!

Next step… create all the email accounts for everyone, then move the DNS for all our domains Exchange will service over to Gradwell.com so I can modify the MX record easily. This is probably the scariest part, as all email and web access will probably drop for a while as the propagation takes place all around the world.