A move from Outlook 2000 to Outlook 2007 at work before Christmas resulted in deactivated Outlook rules and messages like the following when I tried reactivating them:
One or more rules could not be uploaded to Exchange server and have been deactivated. This could be because some of the parameters are not supported or there is insufficient space to store all your rules.
The cause is a 32 KB size limitation for all rules associated with your Exchange server account prior to Exchange 2007. With the latter, the default size increases to 64 KB and can be increased further to 256 KB by manual intervention. This wouldn’t be a big issue if you had the option to store rules locally on your own PC but that was removed after Outlook 2000, therefore explaining why I first encountered it when I did. Microsoft has a useful article on their support website containing suggested remedies and they aren’t all as extreme as deleting some rules either. Consolidation and shortening of rule names are other suggestions and you should never discount how much space the “run on this machine only” parameter takes up either. Still, it’s an odd design decision that caused this but I suppose that it wouldn’t the first made by Microsoft and it may not be the last either.