Outlook Error - Your server administrator has limited the number of items you can open simultaneously.

One of my customers running a custom line of business application called Office Automator by Office Automation which integrates with Microsoft Outlook experienced problems were experienced when sending emails.  The Outlook client was configured to use a direct RPC to the Exchange server.  The error users were experiencing was as follows:

Error No: -2147220731

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.

The customer was running a single Exchange Server 2010 SP1 multi role in the backend. It is important to note that the user had multiple Outlook sessions open having Outlook running locally on their desktop computer and a second session initiated as a RemoteApp from a remote desktop session host server.

In addition to the error being generated on the Outlook client, the following error was also being generated in the Exchange 2010 application logs on the mailbox server role.

Event ID: 9646
Source: MSExchangeIS

Mapi session 'GUID' exceeded the maximum of 250 objects of type "objtMessage".

This error was resolved by increasing the amount of maximum objtMessage calls a single MAPI session for a mailbox can create from 250 to 500.  This was done by making the following registry key changes:

1. On the Microsoft Exchange Mailbox Server exhibiting the error, open the Registry Editor.
2. Go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3. Right-click ParametersSystem, point to New, and then click Key.
4. Type MaxObjsPerMapiSession, and then press ENTER to name the new subkey.
5. Right-click MaxObjsPerMapiSession, click New, and then click DWORD Value.
6. Type objtMessage, and then press ENTER to name the object.
7. Right-click objtMessage, and then click Modify.
8. In the Value data box, type the number of objects to limit this entry to, and then click OK.
9. Close the Registry Editor.

As you see below I increased the limit to 500.

 

For more information on tweaking Exchange Store Limits in Exchange 2010 please review the following TechNet article:

http://technet.microsoft.com/en-us/library/ff477612(v=exchg.141).aspx

Hope this post has been helpful!