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Is Your Outlook Slow? You May Have Exceeded Exchange’s Single-Folder Item limit




Has your Exchange-based Outlook mail client performance gotten slower over time? For example, is your Outlook Search getting slower? Or do you often get a message saying something like “Requesting data from Microsoft Exchange Server” that is slow to clear before you see your mail update?

If so, you may have a problem that most people are not aware of: you may have reached Exchange’s single-folder item count limit. The good news is, if you have exceeded that limit, it can be fixed fairly easily as I discuss below, and your speed should come back.

What is this Limit?

Exchange’s single-folder item count limit is different from Exchange’s mailbox storage limit. You might still have lots of space, but if you have too many e-mail items in one folder, the slow-down will occur. That’s because it’s based only on item count, not size, and that count is not that hard to reach well before you run out of mailbox storage space. The fix is simple: spread your mail across more folders or subfolders; or archive or delete your mail off the server. More on how to do that smartly, below.

What are the Limits? 

Microsoft Exchange Server 2007 has a single-folder count limit of around 20,000 items; and Exchange Server 2010 has a limit of around 100,000 items. That means Exchange Server 2010 has pretty much eliminated the problem since most users will probably hit their mailbox storage size limit well before reaching 100,000 items in one folder. Big Sur’s Hosted Exchange leverages Microsoft Exchange 2010. Big Sur’s Recommendation is to try to keep a folder around 75,000 and no more.

How do you Know You Are Over?

What happens when you reach the item limit—how do you know you are exceeding it? Well, unlike when you hit your space limit, you won’t get a warning dialog box and you won’t be prevented from sending mail if you go well over it. When you start to go over what the system can handle, Outlook just starts to degrade—in other words Outlook gets slower, particularly when searching or sorting mail. The indexes behind the list views in Outlook just get overtaxed and start to slow down. That Microsoft article also says that you may see the following messages appear as Outlook seems to take longer and longer to respond:

“Requesting data from Microsoft Exchange Server” or “Outlook is retrieving data from the Microsoft Exchange Server”

If you suspect you are having this issue, note that you can see the item count for your currently active folder by looking in the lower left-hand corner of the Outlook window; checking that and comparing to the numbers above will help you determine if you are over the limit.

What can you do?

The easiest thing to do is delete email. We are not totally a fan of Outlook based archiving as those archive databases (.PST’s) are prone to corruption. Take a look @ your Deleted Items, do you have tons of mail in there? Do you really need it all?


Another thing I have recommended to customers is create folders that split the folders by Year and move everything out of the inbox into those folders. We often see people with 300,000+ items in their inbox, and its pretty common for us to create a folder structure such as the above, and 9 out of 10 times, that action alone can solve alot of problems. Remember, try not to keep any one folder with more then 75,000 items in it. But very important, once you do housecleaning – please run a compact of your OST file, this can take HOURS to complete. I made an article and a video on this topic. Its located here -> http://support.bigsurtech.com/2013/08/big-sur-tip-how-to-compact-your-outlook-datafile/ – Once you purge or delete a bunch of stuff, the compact can bring the space of the .OST down and it makes it run cleanly and perform far better.

I want to delete email, But what if I need it?

Big Sur has a few options for you, the easiest one is leveraging our email archive. If you have Hosted Exchange with us, its $5.00 per mailbox per month, info on this solution is here -> https://bigsurtech.wpengine.com/it-solutions/big-sur-email-archive – It will keep a copy of everything in the back-end archive. We can then give you access to retrieve old and delted emails. Then once we have the archive enabled, we can delete all email form the system older then 3 years. Now your mailbox which had 900,000 items and has a cache file of 50 GIG’s is now less then 100,000 items and its only 5 GIG’s. This also can save you money on backup charges, and storage costs.

In Closing…

There are a few things to remember… IF you dont delete email – Outlook storage will grow, it will come to a point where it gets so large that outlook will have poor performance. No amount of Memory, Hard drive Space, or CPU Horsepower can solve that. Outlook needs to be groomed. You need to have folders with less then 75,000 items in it. And most importantly, Delete old emails – If you want to keep them as a just in case – lets talk about email archive. Still not sure about your options, Give us a call.