HomeSoftware TitlesMicrosoft Outlook 2010How to troubleshoot performance issues in Outlook 2010

6.1. How to troubleshoot performance issues in Outlook 2010

Firstly the following can temporarily cause Outlook to be slow:

Is Antivirus software running? Is Windows Desktop Search Indexing? Is Outlook reconciling the OST or PST file following an issue? Please see related page for further information on these topics.

Antivirus programs and personal firewall programs can change or remove packets, rewrite files on disk, or alter the memory of running programs. All of these can cause problems for Outlook. Disable any antivirus programs and personal firewall programs.

AVG AntiVirus is known to cause problems with Outlook and the Outlook Connector. You need to disable the email scanning portion of AVG antivirus for Outlook to work properly. On most versions of AVG, the systray icon will change to a gray color when this is done.

The Google Desktop Search can cause excessive memory use and hangs when used with the Outlook Connector. You should uninstall it to confirm that it is causing your problem. If it is not the cause, you may reinstall it.

Are you running the latest version of Outlook 2010?

We recommend that you install the latest applicable Service Packs (SP) and hotfix packages. For more information about the latest applicable updates, click the following article number to view the article in the Microsoft Knowledge Base:

2625547 How to install the latest applicable updates for Microsoft Outlook (US English only)
If running Kerio Connect Client, disable Outlook Instant Search

In Outlook 2007, there is an instant search option which can cause slowness in Outlook with KOFF. We have noticed significant improvements after disabling the Outlook instant search feature. Instructions are available on the following link:

Note that KOFF has its own built-in searching, and does not depend on the Outlook Instant Search feature.

If running Kerio Connect Client, disable 'Group by' view

In Outlook 2003 and above, there is an option to show emails in groups. If you find that folders such as the 'Sent Items' take an excessive time to load, it is recommended to disable the 'group by' view, which is the view option, 'Show in groups'.

Do you have a large .pst file or .ost file?

If you have a large .pst or .ost file, you may experience application pauses while you perform typical operations in Outlook. These typical operations include reading email messages, moving email messages, and deleting email messages.

When you use Outlook 2010, the following .ost size guidelines generally apply: 

With Outlook 2010, the maximum size for a .pst file is now 50 GB. The default maximum size for a Unicode .pst or .ost file is approximately 50 GB. The following Microsoft Knowledge Base article describes how to increase the maximum size of a .pst or .ost file:

832925 How to configure the size limit for both (.pst) and (.ost) files in Outlook 2007 and in Outlook 2003

The following blog post describes how to reduce the size of your local data file by using synchronization filters:

This is a stop-gap solution and is provided here for reference if you cannot reduce the size of your mailbox. For example, you may be unable to reduce the size of your mailbox if you have to maintain an archive of all email messages, both sent and received, over a time span of several years.

Do you have many items in a single folder?

If you use .ost or .pst files

If you have lots of items in any single folder, you may experience performance issues during certain operations in Outlook while you use local data files. If you use Outlook to connect to a mailbox that is located on a Microsoft Exchange Server and use Cached Exchange Mode, Outlook synchronizes email and other items to an Offline Outlook Data (.ost) file. If you use Outlook to connect to other email accounts, such as POP3 or IMAP, Outlook stores email and other items to a local Outlook Data (.pst) file. These performance issues are especially noticeable when you switch into and out of folders that contain a large number of items. 

If you have more than 50,000 items in a single folder, views other than Arrange By: Date can be slower. We recommend that you move several items in these larger folders to separate folders in the same store or to an archive store and that you use Arrange By: Date when you run Outlook 2010.

If you connect to Exchange in Online mode

If you are not using Cached Exchange mode, you should review one of the following resources. These resources document some performance issues on an Exchange server that has high item counts and restricted views. Additionally, the resources discuss how these performance issues might affect the overall client user experience.

For more information about poor performance when you are working with an Exchange Server mailbox folder that contains lots of items, click the following article number to view the article in the Microsoft Knowledge Base:  

905803 Outlook users experience poor performance when they work with a folder that contains many items on a server that is running Exchange

For information about the performance effect of high item counts and restricted views, visit the following Microsoft web sites:

Understanding the Performance Impact of High Item Counts and Restricted Views
Understanding Database and Log Performance Factors

Do you have any nonessential add-ins or out-of-date add-ins installed in Outlook?

If you have nonessential add-ins installed, you may want to remove them from Outlook. To view the add-ins that are installed, follow these steps:
  1. In Outlook, click the File tab.
  2. Click Options, and then click Add-ins to display a list of the COM add-ins that are installed.
By default, the following COM add-ins are included in Office 2010:
  • Microsoft Access Outlook Add-in for Data Collection and Publishing
  • Microsoft Exchange Add-in
  • Microsoft Outlook Social Connector
  • Microsoft SharePoint Workspace Proxy for Outlook Add-in
  • Microsoft SharePoint Server Colleague Import Add-in
  • Microsoft VBA for Outlook Add-in
  • OneNote Notes about Outlook Items
  • Windows Search Email Indexer
Any other add-ins that are listed under COM add-ins were installed by other software.

To determine whether the performance problem is caused by add-ins, run Outlook in safe mode. To do this, press and hold Ctrl when you start Outlook. When Outlook starts in safe mode, all COM add-ins and Exchange Server client extensions are disabled.

If the problem no longer occurs when Outlook is running in safe mode, it is likely that one of the add-ins is causing the performance issue. To troubleshoot possible problems that are caused by COM add-ins or Exchange Server client extensions, disable any items that you do not use regularly. Then, restart Outlook. If that does not resolve the problem, disable the remaining add-ins one by one. If that does not resolve the problem, the issue may not be caused by an add-in.

To disable COM add-ins, follow these steps:
  1. In Outlook, click the File tab.
  2. Click Options, and then click Add-ins to display a list of the COM add-ins that are installed.
  3. Select COM Add-ins in the Manage list, and then click Go.
  4. In the COM Add-Ins dialog box, click to clear the check boxes for any COM add-ins that you want to disable.
  5. Click OK, and then restart Outlook.

Reset Cache for Exchange, IMAP or KOFF

1. Close Outlook
2. Go to Control Panel -> mail -> accounts -> Kerio properties -> maintenance -> clear cache.
Re-create the offline Outlook Data File (.ost). See related article if you're unsure how to do this.

Enable AutoArchive

Your Microsoft Outlook mailbox grows as you create and receive items. To manage the space in your mailbox or on the mail server you are using, you can move old items that are important, but rarely used, to an archive location. This storage process occurs automatically with AutoArchive, but you can customize most of the default settings. For further information please see related article.

Repair the Application from the Software Control Panel

The following should be done if the above has not worked:

Create a new Profile

The Outlook profile is a frequent cause of problems. Many problems can be resolved by creating a new profile.

To create a new Outlook profile:

  1. Open Control Panel -> Mail.
  2. Open "Show Profiles". You will see a list of your current profiles.
  3. Set "When starting Microsoft Office Outlook, use this profile" to Prompt for a profile to be used.
  4. Click "Add" to create a new profile. Follow the steps and create an account of Additional Type, Kerio MailServer
  5. Please make sure that you set "Default Delivery Location" to Kerio Outlook Connector Store. This is critical for Kerio Outlook Connector to function properly!
  6. Complete the account with the information you have used to create prior Outlook Connector accounts
  7. Do not create additional POP3 or IMAP accounts in this profile. This is not supported.

Note: When you create a new profile, you will not lose any mail, calendars or contacts. Your original profile will continue to be available. Your profile-specific settings will not be available in the new profile; these include default views, sorting options, and distribution lists.

Repair Outlook Data Files (.pst and .ost)


If your Microsoft Outlook Data File (.pst and .ost) won't open or you suspect that the data file is damaged, use the Inbox Repair tool (Scanpst.exe) to diagnose and repair errors in the file. The Inbox Repair tool checks the Outlook Data Files on your computer to see if they're in good shape.

  1. Exit Outlook, and browse to <drive>:\Program Files — or, if you see a Program Files (x86) folder on the same drive, browse to that instead. For example, C:\Program Files or C:\Program Files (x86).

  2. In the Search box, type Scanpst.exe.

If the search doesn't find Scanpst.exe, try searching in the alternative folder mentioned in step 2, above — Program Files or Program Files (x86).

  1. Double-click Scanpst.exe.

  2. In the Enter the name of the file you want to scan box, enter the name of the .pst file you want the tool to check, or click Browse to select the file.

  3. By default, a new log file is created during the scan. Or, you can click Options and choose not to have a log created, or to have the results appended to an existing log file.

  4. Click Start.

If the scan finds errors, you're prompted to start the repair process to fix them.

The scan creates a backup file during the repair process. To change the default name or location of this backup file, in the Enter name of backup file box, enter a new name, or click Browse to select the file you want to use.

  1. Click Repair.

    A copy of the log file is saved to the same folder as the .pst file.

  2. Start Outlook with the profile that contains the Outlook Data File that you repaired.

  3. Switch to the Folder List view in the Folder Pane by pressing Ctrl+6.

In the Folder Pane, you might see a folder named Recovered Personal Folders that contains your default Outlook folders or a Lost and Found folder. Although the repair process might recreate some of the folders, they may be empty. The Lost and Found folder contains any folders and items recovered by the repair tool that Outlook can't place in their original structure.

You can create an Outlook Data File, and drag the items in the Lost and Found folder into the new data file. After you've moved all the items, you can remove the Recovered Personal Folders (.pst) file. This includes the Lost and Found folder.

If you can open the original Outlook Data File, you may be able to recover additional items. The Inbox Repair tool creates a backup file with the same name as the original, but with a .bak extension, and saves it in the same folder. You may be able to recover items from the backup file that the Inbox Repair tool couldn't recover.

To recover items from the backup (.bak) file, make a copy of it and give the copy a new name with a .pst extension, such as bak.pst. Import the bak.pst file into Outlook, and then use the Import and Export Wizard to import any additional recovered items into the newly created .pst file.

See how to import a .pst file by reading Import Outlook items from an Outlook Data File (.pst).

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