We are running SBS 2008 with Exchange 2007. Everything was working fine and then all of a sudden we stopped getting mail. I did a reboot on the server and it started to work. Then about 4 hours later it stopped. Did another reboot and it started working. This has been going on for the past few days where I have to reboot the server a few times a day to get the mail to flow.
I checked the event logs and there are no errors relating to Exchange.
Another thing that I might add is that there is only 3.5GB free on the c drive. All the mail and other data is stored on d with plenty of free space. Don't know if this has anything to do with it, but thought I should mention it.