Since we've updated to 2007 email notifications have stopped working.

Can anyone suggest where to start troubleshooting?

The "Send Test Email" button in the "Email Notification Services" seems to work when you look at the test results - problem is, the email never arrives.

I understand these types of notifications have nothing to do with the Email Service, that polls a mailbox looking for items from which Bugs, etc can be created.

Any ideas, anyone??