Article ID: 2441551 - View products that this article applies to.
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When you use Microsoft Outlook together with Microsoft Office 365, the following issues may occur:
This issue may occur for many reasons. This issue may be caused by an Exchange Online server issue. Sign in to the Microsoft Office 365 portal with your admin credentials, and then click Service Health on the Admin Home page to determine whether other customers are experiencing the same issue. If other customers are experiencing the issue, the issue should go away when the service-interrupting event is resolved.
Also, determine whether there are any local network issues that might be causing the problem, such as issues with your local proxy server, firewall, or Internet service provider.
To determine the specific cause and to resolve the issue, use the methods that are described in this article.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756To troubleshoot this issue, use one or more of the following methods:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
Method 1: Enable Cached Exchange ModeYou can try to improve performance by making sure that Cached Exchange Mode is enabled. To do this, follow these steps, depending on the version of Outlook that you are using:
Method 2: Determine global catalog usageBy default, if Outlook can't access the Offline Address Book, it uses the online global address list (GAL). This can slow performance. To determine whether this is the case, click the Address Book icon in Outlook, right-click the GAL, and then click Properties. If the properties show the fully qualified domain name (FQDN) of a server instead of a local folder path, Outlook is using the online GAL instead of the Offline Address Book. If this is the case, you can download the Offline Address Book (OAB).
Method 3: Download the Offline Address BookMake sure that you can download the Offline Address Book (OAB). To do this, follow these steps:
Method 4: Check the OST file sizeMake sure that offline OST file in Outlook isn't too large. A large OST file may indicate corruption or fragmentation of the file. This can affect performance.
Method 5: Reduce the number of items in critical folders
If you continue to have problems, make sure that there are not too many items saved in the Calendar, Contacts, Inbox, and Sent Items folders. If the Inbox folder or the Sent Items folder contains more than 20,000 items, or if the Calendar folder or the Contacts folder contains more than 5,000 items, the performance of Outlook can be affected.
Method 6: Disable add-ins
If Outlook is already using the Offline Address Book, or if the problem continues after you download the Office Address Book, an add-in may be causing Outlook to respond slowly. In this case, try to disable add-ins in Outlook. To do this, follow these steps, depending on the version of Outlook that you are using.
Method 7: Start in safe modeIf the problem continues, try restarting Outlook in safe mode by running the following command from the Run box or from the Start Search box on the Start menu:
If performance improves, check again to make sure that you disabled any Outlook add-ins that may affect performance.
Method 8: Disable Lync Online integration
If Outlook is integrated with Microsoft Lync Online in your Office 365 environment, the integration may be affecting Outlook’s performance. To disable Lync Online integration with Outlook, follow these steps:
Method 9: Disable email scannersEmail scanners, search programs such as Google desktop, and other services that scan the Outlook mailbox may also affect the performance of Outlook. Try disabling any such programs or services, and then see whether Outlook performance improves. You can determine which programs and services are currently running by pressing CTRL+ALT+DEL to open Task Manager. Some antivirus software can also scan incoming email messages. Make sure that you talk to the IT administrator before you disable any antivirus software on your computer
Method 10: Check Group Policy settingsIf your organization’s Exchange environment is governed by Group Policy, you should determine whether there are any group policies specific to Outlook that apply to the users who are experiencing the poor performance. If there are, determine whether you can reproduce the performance issues from another computer that does not receive that Group Policy setting. By doing this, you can determine whether the policy is contributing to the poor performance. If this is the case, you can amend or eliminate the policy setting.
Method 11: Repair OutlookIf the problems continue, try to repair Outlook on the computer where the problems occur. To do this, follow these steps:
Method 12: Cache additional mailboxes
Method 13: Decrease the synchronization frequency for Outlook 2010 items
Still need help? Go to the Office 365 Community
Article ID: 2441551 - Last Review: September 11, 2013 - Revision: 32.0