Over the years, some Exchange users have learned the hard way that there is a limit to how many mailbox rules they can define. The limit is based upon the cumulative size of all the rules associated with a mailbox, rather than the number of rules. Under Exchange 2003, mailbox rules were capped at 32KB. With Exchange 2007, that cap has doubled to 64KB, which generally translates to about 100-150 rules, depending upon how big they are (even the size of the rule name counts towards this). You know you’ve hit that cap when Outlook gives you an error such as the following:
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.
So, what is an Exchange user to do when confronted by this? There are two things to try:
- First, try to reduce the total size of your rules. This Microsoft KnowledgeBase article provides excellent tips on how to do so.
- If that doesn’t do the trick, contact your friendly neighborhood Exchange administrator (for AEMS users, that means going through the Help Desk) and ask him/her to bump up your rules quota. That’s right, Exchange 2007 added the ability for Exchange administrators to modify this quota on a per-user basis*.
“So,” I hear you cry, “given the availability of the second option, why should I bother with the first?”
That is a perfectly valid question, and one for which I can offer an equally valid response: efficiency. The more mailbox rules you have, the more processing each message in your mailbox must endure. The more rules you have, the more processing and memory overhead is incurred. Individually, it doesn’t amount to much, but aggregated over thousands of users, it can mean a noticable impact on performance. Besides, if you have enough rules that you bump into your rules quota, odds are that there is a way to accomplish what you are trying to do more efficiently.
While we are on the subject of server performance, there are two other things that I should point out that can impact performance, not just for you, but for all users on your server:
- Don’t keep to many items in your Inbox. Delete them or file them into another folder. Having many thousands of items in your inbox will seriously degrade server performance. Keep the Inbox (and all of the other “default” folders in your mailbox) as lean as you practically can. This is basic mailbox hygiene.
- If you use an Outlook add-in and notice that it seems to slow down your connectivity to the server, please remove it. Odds are that it is impacting the experience of other users as well. I’ve seen Exchange servers brought to their knees by misbehaving Outlook add-ins. It isn’t pretty.
* A note for other Exchange administrators who might be reading this: You might be wondering how to go about changing the rules quota. It is quite simple, really:
Set-Mailbox someuser -RulesQuota:128KB