Exchange 5.5 Out Of Office/Rules problem

We have an exchange 5.5 sp4 server with outlook 2000 clients. We’ve just noticed that out of office/rules don’t appear to be working. I’ve rebooted the server with no joy.

I’ve just created a new test account and out of office/rules seem to work fine.

So there seems to be issues with the existing mailboxes (these were migrated from an old server some time ago). Any ideas….??