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

October 5, 2012

Has your Exchange-based Outlook mail client performance gotten slower over time? For example, is 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.

Note this is a problem only on older Exchange servers—Microsoft has mostly fixed this on the newest ones. But also note that even though you may have a newer version of Outlook, the Exchange Server version your company runs behind your Outlook is invisible to you, and it could be quite old and so still subject to this issue. Many IT departments are slow to upgrade their server software, so check with your IT department to confirm the version (more on which versions are effected below).

Before I explain more details on how this limit works, how to identify it, and specific strategies to fix it, let me first give you some background on why 1MTD or MYN users should be particularly aware of this.

Why 1MTD and MYN Users Should Know This

As you may know, my primary recommendation in 1MTD and MYN for filing mail is to file all saved Outlook e-mail into one folder called the Processed Mail folder. Nearly all my books and classes discuss the huge benefits of doing this, so I won’t repeat the reasons here (for more online information about how I use the Processed Mail folder, see this article).

But obviously that single-folder filing approach could make you more prone to reaching the Exchange single-folder item count limit (again, if using an old Exchange server); any one folder loaded with lots of items, like the Processed Mail folder, can cause the problem. It’s a bit ironic that a filing best-practice that will make you more productive could lead to a technical server issue.

And even if you are not using the Processed Mail folder approach, but perhaps you are storing lots of old mail in your Inbox, then you could still be impacted by this issue; the Inbox is subject to the same limits.

What are the Limits? How Old a Server?

Are you likely to hit this? How many items are too many for a single folder? Microsoft has an article on this and it states the limit is directly determined by the version of your Exchange Server.

According to that article, if you have Exchange Server 2003 or 2000, the limit will be somewhere around 2,500 to 5,000 items in one folder. That’s not a lot of mail and so that number will be easy to reach if your company is using those older versions of Exchange and you are filing a lot of mail in one folder.

Newer servers are better. Links at the bottom of the article I referenced above lead to other articles that state their limits. Apparently 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.

Again, you have to contact your IT department to find out your Exchange version. Unfortunately it’s not displayed in the Outlook client and it’s not the same as your Outlook version number.

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.

Rather, performance of 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.

1MTD or MYN Strategies to Fix it

If you are a 1MTD or MYN user, and have confirmed you have this issue, then it’s time to decrease the number of items in your Processed Mail folder. How? Well, you can 1) delete or archive old mail off the server from that folder, or 2) you can spread the mail across one or more additional Processed Mail folders still on the server. Which to do depends on how large your Exchange storage limit is.

If you have a generous Exchange storage allocation, you can probably do number 2 and spread your mail across multiple Processed Mail folders on the server (just alter the names to indicate the date range). By putting them on the server you get the benefits of mobile access and corporate backup.

But if your mailbox storage size limit is tight relative to the count limit, then you probably want to do number 1, and delete items or use off-server archiving. On Windows you’d probably use a Personal Folders (PST file) approach to archive mail; see Appendix A and B of my Outlook book for strategies for archiving mail into local folders. Or, if available, start using the new Personal Archives feature that some companies are slowly starting to roll out with their Exchange 2010; that will solve the issue too.

Fine Tuning after a Processed Mail Folder Fix

After adjusting your Processed Mail folder, don’t forget to also check your Sent Items folder count, as it can build up easily. You may need to archive or split it up as well.

Also, there can be tighter limits for the Contacts and Calendar folders that could have similar effects. In the articles above Microsoft states that to maintain performance on Exchange 2007, you want to keep Contacts and Calendar folders under 5000 items each, and that for Exchange 2010 the limit for each is 10,000 items. Apparently in Exchange 2003, those folders have the same limits as the mail folders (2500 to 5000 items).

After you make the fixes above, keep in mind that Outlook Instant Search can be configured to search all your folders by default; so if you do transition to multiple Processed Mail folders, you will probably want to make that search setting. See the end of chapter 5 in my Outlook book for a discussion of how to make settings like that.

Also, if you have multiple Processed Mail folders on the Exchange server, you may want to start using my All Mail Search Folder that I discuss in an older blog article so that you can view and scroll through mail on multiple folders as if they were in one folder. There are lots of other benefits of using the All Mail Search Folder, so take a look at that article.

Wrap Up

That’s it; that’s the problem and solution. Luckily the problem is unlikely to occur on the newest versions of Exchange, and so there is a good chance it will be less common as time passes and servers are upgraded. But if you are having slow Outlook performance now, this could be why.


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

  1. Manan Choksi says:

    i always cursed my ISP for a slow internet connection when this problem happened! Thanks for sharing this.

    I think based on the information above it would be better for me to force my vendor to upgrade to a Exchange 2010 then all the subdivision of folders to 5,000 limit.

  2. adrian says:

    can we have an update to this article…related to the use of the cloud? I was fine with my search functions until we went to the microsoft cloud. now it takes forever to find the related emails I’m searching for.

    • Michael Linenberger says:

      Adrian, I don’t think I can help you because the “Microsoft Cloud” equals “Exchange Server”; there is no difference. They just renamed it. I’d say something else happened in your environment. Like maybe your IT folks switched from one Exchange Server to another, and the latter one is having issues. I’d bring this up with your IT folks.

  3. YeChan Ahn says:

    This worked for me!
    I distributed all the mails in inbox to another folders, under 2000 mails a folder.
    And updating status has been gone and it works very well now.



  4. Rajeev Saxena says:

    will the outlook slow down if we run the update-mailboxstore command for all the databases in exchange 2013.

  5. But if you are having slow Outlook performance now is good

  6. Liz Redwing says:

    Could this also cause my Outlook to crash? I use Microsoft Exchange across 3 devices (so I can sync everything) and the other day Outlook started crashing on 2 of them (& on the third, my phone, it simply limits the number of e-mails I can receive/see). I have a feeling that there is a LOT of mail on my server – mail that I’ve deleted but that still sits there until … I don’t know when. and I have no idea how to change those settings. I’m fairly certain there is a lot of mail buildup since I am currently able to work in web Outlook and I noticed a lot of ‘new’ mail there that I deleted at least a couple of weeks ago (but probably more).

  7. David Fisher says:

    We have created an application: “Yearly Message Filling”. It scans your Outlook folders and categorizes the emails by year or year/month under new folders. They are named after the year or the year/month the emails were created. The end result is that emails are distributed under multiple folders that are not overcrowded with messages. And Outlook can run faster again!

    We have a free version which you can try:

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