When you try to access folders in a secondary Microsoft Exchange Server mailbox that was added to your Microsoft Outlook profile, you may experience random performance problems. For example, you may experience the following symptoms:
On a server that is running Microsoft Exchange Server, an event that resembles the following event is logged in the Application log:
Event Type: Error
Event Source: MSExchangeIS
Event Category: General
Event ID: 9646
Closing Mapi session "/o=Organization/ou=Administrative Group/cn=Recipients/cn=recipient" because it exceeded the maximum of 500 objects of type "objtFolder".
Additionally, you may find errors that resemble the following in the synchronization log messages in the Outlook Sync Issues folder:
13:22:28 Synchronizer Version 12.0.6529
13:22:28 Synchronizing Mailbox 'TeamShared'
13:22:28 Synchronizing Hierarchy
13:22:28 Error Synchronizing Hierarchy for Mailbox 'TeamShared'
13:22:28 Your server administrator has limited the number of items you can open simultaneously. Try closing messages you have opened or removing attachments and images from unsent messages you are composing.
13:22:28 Microsoft Exchange Information Store
13:22:28 For more information on this failure, click the URL below:
13:22:28 Error synchronizing folder
13:22:31 Synchronizing local changes in folder 'TeamShared - Level1'
13:22:31 Error synchronizing folder
13:22:31 Your server administrator has limited the number of items you can open simultaneously. Try closing messages you have opened or removing attachments and images from unsent messages you are composing.
13:22:31 Microsoft Exchange Information Store
13:22:31 For more information on this failure, click the URL below:
When this issue occurred, the following synchronization error numbers have also been seen in synchronization messages in the Sync Issues folder:
Note You must select the Folder List module on the Navigation pane to see the \Sync Issues folder in your mailbox.
This problem may occur if the following conditions are true:
This problem occurs because Outlook 2010 locally caches (in your Outlook data file [.ost]) all folders to which you have access in the secondary mailbox. This is a change from earlier versions of Outlook. Outlook 2003 does not cache any shared folders, and by default, Outlook 2007 caches only those shared folders that do not contain email (such as Calendar, Contacts, and Tasks).
Note In Outlook 2007, this problem is more likely to occur if you also have the following registry data configured on your Outlook client.
Key: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Cached Mode
To resolve this problem, use one of the following workarounds.
Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows XP and Windows Vista
Method 1: Reduce the number of folders in the Shared mailbox
The best solution to this issue is to reduce the number of mail folders in the shared mailbox, especially if your mailboxes are in the Office 365 environment. Additional methods 2 and 3 in this article advise you to turn off the caching of mail folders or all folders in the shared mailbox. These solutions do work, but if your mailbox is in the Office 365 environment, the advice (Method 12) in the following article is to enable the caching of shared mail folders.
2441551 Outlook performance is slow in the Office 365 environment
Because the methods in this article may contradict the advice in article 2441551, the best overall solution is to reduce the total number of folders in the shared mailbox.
Method 2: Disable caching of all shared folders
Outlook 2010 and Outlook 2013
To disable the caching of all shared folders, follow these steps:
To disable the caching of all shared folders, follow these steps:
After you make this change, none of the shared folders in the secondary mailbox will be available to you in Outlook when you are working offline. However, all folders in the primary mailbox will still be available to you when you are working offline.
For more information about disabling the download shared folders by using a Group Policy setting, click the following article number to view the article in the Microsoft Knowledge Base:
982697 By default, shared mail folders are downloaded in Cached mode in Outlook 2010 and Outlook 2013
Method 3: Change the configuration of the secondary Exchange mailbox to a second Exchange account in your profile
Outlook 2010 and Outlook 2013 only
If you want to cache all folders in the secondary Exchange mailbox, follow these steps to modify your Outlook profile so that the secondary mailbox is added as a second Exchange account.
Note To follow these steps, you must either know the password for the account of the secondary mailbox or you must have full mailbox permissions to the account for the secondary mailbox. See your Exchange Server administrator for this information or permissions.
Note If your account does not have full mailbox permissions to the secondary mailbox, you will be prompted for the account credentials to the secondary mailbox.
You may experience the following specific issues when you use Outlook 2010 after you make the configuration changes that are specified in this "Method 3".
When you add additional mailboxes to your Outlook profile and enable caching of the shared mailbox folders, Outlook individually registers every folder in the cached mailbox. Each of these registered folders counts toward the objtFolder type limit on the Exchange Server. As stated in the 9646 event that is shown in the "Symptoms" section of this article, the default limit for objtFolder objects it 500. If you cache one or more shared folders that contain several hundred folders, this limit can be exhausted. When this occurs, you may experience the problems described in the "Symptoms" section of this article.
Additionally, a large number of Public Folder favorites can also contribute to exhausting the objtFolder object limit. For more information on errors that you may encounter when synchronizing a large number of Public Folders, click the following article number to view the article in the Microsoft Knowledge Base:
2494570 You receive "not enough memory" errors in Outlook when you have lots of cached public folders
For more information on the maximum allowed share of server resources on Microsoft Exchange Server 2007, visit the following Microsoft web site:
For more information on Exchange Server 2010 mailbox store session limits, visit the following Microsoft web sites: