I have a problem on a server where as when you go to OWA and try and send a message to a distribution list it can't resolve the names included in this list so won't let you send. The individual address's in the list all work, when an email gets sent from an external source to the distribution list it works, just internally they can't send to the distribution list, from outlook and webmail.
The server is Exchange 2k7 SP3. It was from a migration. The previous exchange server wasn't removed correctly and I had to manually remove this. It is completely gone now from what I can see.