Article ID: 980049 - View products that this article applies to.
You cannot use POP3 or IMAP4 to connect to a Microsoft Exchange Server 2010 mailbox through Microsoft Office Outlook Web Access. When you try to connect, you receive following error message:
If you click Show details, you see that the following exception causes the error:
A problem occurred while you were trying to use your mailbox.
Microsoft.Exchange.Data.Storage.TooManyObjectsOpenedExceptionIf you try to use a Telnet connection to try to connect to the mailbox by using POP or IMAP, you receive the following error message:
The server that is running Exchange Server 2010 logs an error in the Application log that resembles the following:
Note The following changes do not resolve this issue:
Log Name: Application
Event ID: 9646
Task Category: General
Mapi session "/o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=E-mailUser" exceeded the maximum of 16 objects of type "session".
<Provider Name="MSExchangeIS" />
<TimeCreated SystemTime="SystemTime" />
<Data>/o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn= E-mailUser </Data>
This issue occurs because the Exchange 2010 Store limits the number of non-MAPI sessions that other services generate, such as IMAP, POP, Outlook Web Access, Microsoft Exchange ActiveSync (EAS), or Exchange Web Services (EWS). By default, sessions per user are limited to 32, and service sessions per user are limited to 16.
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 resolve this issue, first determine whether this situation is caused by a different issue. If this is not the case, then increase the limit that your organization requires for non-MAPI sessions. To do this, follow these steps:
(https://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
For more information about how to set limits for sessions, visit the following TechNet Web pages:
Set Connection Limits for IMAP4
Set Connection Limits for POP3
Article ID: 980049 - Last Review: September 5, 2013 - Revision: 2.0