I am running Exchange 2007 SP1 on Windows SBS 2008 and it has been running smoothly for several months. Today, however, 2 things (presumably connected) happened:
(1) Incoming messages from external organisations/addresses are seemingly disappearing -- they are not delivered to recipients, and external senders don't get any kind of bounce message. Obviously this is very concerning since I don't know where those messages may have gone. Incoming messages from within the organisation *are* delivered fine, and outgoing messages sent "to the outside world" are also getting through. So it seems to affect only incoming messages from the Internet.
(2) Mobile devices are no longer syncing via ActiveSync properly. It just says "Connecting..." for a while and then eventually gives up. I also allow connections via IMAP, and same thing happens there. Strangely, though, I noticed that my mobile device has synced occasionally from time to time -- after about 2 or 3 hours of it just sitting there, I noticed that as a one-off it did manage to download (internal) messages. When I tried again straight afterwards, it got stuck at "connecting..." again.
I've restarted the whole server and run the Mail Flow Troubleshooter and Best Practices Analyzer. These don't appear to indicate anything different to normal.
The issue with the syncing made me wonder if perhaps the server is being slowed down by some kind of network traffic problem or other resource issue. I'm not aware of anything specific but not really sure how to diagnose these issues. (We are a company of only 4 people and I'm relatively new to Exchange and network admin.)
Thanks for any suggestions anyone has about a fix and/or things to look at!