Couple of customers reported that after upgrading to Microsoft Office Outlook 2007 or Microsoft Office Outlook 2003, they found that some of the rules are disabled and cannot be enabled. Remaining other rules work correctly. Also if you try to enable the disabled rules they receive the following error message:
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.
Why it occurs: This behavior occurs if the rules that are in your mailbox exceed a size of 32 kilobytes (KB). The rules size limit for mailboxes on Microsoft Exchange Server is 32 KB. In Outlook 2003/Outlook 2007, the size of rules has increased mostly to provide support for the Unicode format.
Note The rules size limit for mailboxes in Microsoft Exchange Server 2007 has been increased to a default size of 64 KB per mailbox. The rule limit is now a customizable limit up to 256 KB per mailbox.
Please find the following KB, which helps us how to mitigate this situation and has couple of workarounds for this issue.