A new registry value has been added to the Microsoft Exchange Information Store service that allows an administrator to set a limit on the number of recipients that a mail message can have.

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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:
To set this parameter, perform the following steps:

1.	Start Registry Editor (Regedt32.exe).
2.	Locate the following key in the registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ ParametersSystem Note The above registry key is one path; it has been wrapped for readability.
3.	On the Edit menu, click Add Value, and then add the following registry value: Value Name: Max Recipients on Submit Data Type: REG_DWORD String: A value equal to the maximum number of recipients that you want to allow
4.	Quit Registry Editor.

In Exchange Server 5.5 and earlier, this limit also applies to messages that are transferred into the store by the Internet Mail Service. An event ID 4117 message is logged and the message is moved to the Archive folder. The message is not delivered and it does not send a non-delivery report (NDR).

Note In Exchange 2000 and later, only messages submitted with MAPI are subject to this restriction. To configure recipient limits that work for all messages regardless of how they are submitted, use the setting that is located under Global Settings\Message Delivery in Exchange System Manager.

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If a user attempts to send a message to more recipients than is designated by the Max Recipients on Submit parameter and the user has the new Emsmdb(32).dll, the following error message may be displayed when the user attempts to send the message: If a user attempts to send a message to more recipients than is designated by the Max Recipients on Submit parameter and the user DOES NOT have the new Emsmdb(32).dll, the following error message may be displayed when the user attempts to send the message: Note the following when you add the above registry key:

•	You do not have to stop and restart services for this change to take effect.
•	The number you choose applies to total recipients associated with a message (To+Cc+Bcc=Total).
•	You cannot circumvent the limit by using a personal distribution list; it is evaluated for number of entries before the send.
•	In Exchange Server 5.5 only, server-based distribution lists let you exceed the total number of recipients. You can do this by using the Max Recipients on Submit registry value if you have the correct permissions.

Note The new Emsmdb32.dll file referenced in this article is included in Exchange Server 4.0 SP2 and all later versions of Exchange Server.

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