quote:

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Dear Mr. Ken,

Thank you for posting here.

This behavior may occur if both the following conditions are true:

1. You have installed Exchange Server 2003 Service Pack 1 (SP1) on your
Exchange Server computer.
2. A program that is running on a client computer opens many MAPI sessions
to the Exchange Server computer. The number of MAPI sessions is greater
than the permitted limit.

Exchange Server 2003 SP1 imposes a restriction on the number of permitted
MAPI sessions per user. By default, the maximum number of permitted MAPI
sessions per user is set to a hexadecimal value of 0x20 after you apply
Exchange Server 2003 SP1.

Note A hexadecimal value of 0x20 converts to a decimal value of 32.

RESOLUTION
==========

To resolve this behavior, we recommend that you first investigate if the
MAPI session limit is reached because of potential abuse, because it is
the result of a bug in a client program, or because of client program
design.

If the behavior is triggered by a bug in a client program or by a client
program design, we recommend that you contact the vendor to determine if
you can do either of the following:

- Obtain a fix.

- Grant the View Information Store Status Exchange permission to the
account that the program runs under. Programs that run under an account
that has this permission are not affected by the MAPI sessions per user
limit. To grant the View Information Store Status permission, follow these
steps:

1. In Exchange System Manager, right-click the Exchange Server object or
the mailbox store that you want to grant the permission to, and then click
"Properties".
2. Click the "Security" tab.
3. Click the account that you want to grant the permission to.
If the account is not listed, click "Add", click the account name, click
"Add", and then click "OK".
4. Under the "Allow" column, click to select the "View information store
status" check box if it is not already selected.
5. Click to clear the check boxes for any permissions that are not
required, and then click "OK". You may have to perform this step because
if you clicked "Add" to add the account in step c, every check box in the
"Allow" column is selected.

If you cannot obtain a fix and you cannot configure the account to run with
the View Information Store Status permission, you can adjust the number of
permitted MAPI sessions per user in the registry. If you raise the MAPI
session limit, try to determine the minimum value that you can use so that
the client program can run without problems. If you raise the limit too
high, the client program can potentially affect the performance of the
Exchange Server computer.

MORE INFORMATION
================

To change the value of the maximum permitted MAPI sessions per user from
the default, you can configure the Maximum Allowed Sessions Per User
registry entry. To do this, follow these steps.

Warning If you use Registry Editor incorrectly, you may cause serious
problems that may require you to reinstall your operating system. Microsoft
cannot guarantee that you can solve problems that result from using
Registry Editor incorrectly. Use Registry Editor at your own risk.

1. Click "Start", click "Run", type "regedit" (without the quotation marks)
in the "Open" box, and then click "OK".
2. Locate, and then click the following registry subkey:

"HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\Parameter
sSystem"

3. If the "Maximum Allowed Sessions Per User" entry does not exist, do the
following:

a. On the "Edit" menu, point to "New", and then click "DWORD Value".
b. Type "Maximum Allowed Sessions Per User" (without the quotation marks)
as the entry name, and then press ENTER.

4. Right-click the "Maximum Allowed Sessions Per User" entry, and then
click "Modify".
5. Click "Decimal", type the value that you want to set in the "Value data"
box, and then click "OK".
6. Quit Registry Editor.

Hope this helps. Please let me know if you have any other concerns or
questions. Thanks and have a nice day!

Thanks & Regards,

Lee Li
Microsoft Online Partner Support

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• Some users are more affected than others (some never have problems)
• On the client side Outlook (in cached mode) keeps losing connectivity to the Exchange server and re-establishes it later
• Effectively, every time is re-establishes a connection, an additional session is opened
• After 32 open sessions, additional connections are denied
• The problem seems to re-occurr at specific times
• A network trace shows many retransmissions, out-of-order or duplicate TCP packets between the client and the server
• When Outlook fails, many other applications start to fail as well