Q196818: XFOR: How to Limit Recipients on Outbound SMTP Messages

Article: Q196818
Product(s): Microsoft Exchange
Version(s): WINNT:5.5
Operating System(s): 
Keyword(s): 
Last Modified: 16-APR-1999

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 
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IMPORTANT: This article contains information about editing the registry.
Before you edit the registry, make sure you understand how to restore it if
a problem occurs. For information about how to do this, view the "Restoring
the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key"
Help topic in Regedt32.exe.

SUMMARY
=======

The number of recipients specified in the To field of an SMTP message can not be
limited by Microsoft Exchange Server 5.5. However, the manner in which the
Exchange Server Internet Mail Service processes an SMTP message can be altered
by specifying a maximum number of recipients in a registry entry. The registry
entry setting affects only the outbound mail.

After you implement the registry change, a message exceeding the maximum number
of recipients will be sent by the Internet Mail Service to an SMTP host in
batches. Each batch will include a number of recipients equal to or less than
the maximum number of recipients allowed. See the following More Information
section for details.

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

WARNING: Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee that
problems resulting from the incorrect use of Registry Editor can be solved. Use
Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And
Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete
Information in the Registry" and "Edit Registry Data" Help topics in
Regedt32.exe. Note that you should back up the registry before you edit it. If
you are running Windows NT, you should also update your Emergency Repair Disk
(ERD).

To modify how the Internet Mail Service processes messages based on the number of
recipients, follow these steps:

1. On the Microsoft Exchange Server computer, start Regedt32.exe.

2. Find the following registry key:

  HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/MSExchangeIMC/ 
  Parameters


  NOTE: The above is one path; it has been wrapped for readability.

3. On the Edit/Add value menu, add the following:

  Value Name: MaxRecipients
  Data Type: REG_DWORD
  Data Value: Enter the maximum number of recipients that will be allowed
  on a single transmission of an SMTP message.


4. Exit Regedt32, and restart the Internet Mail Service.

The MaxRecipients registry entry will affect the Internet Mail Service's behavior
in the following way:

- Suppose the MaxRecipients hex value is set to 0xFA. This translates to a
  decimal value of 250, which is the maximum number of recipients that the
  Internet Mail Service will process in an initial transmission of a message
  which contains more than 250 recipients in the To field.

- If a message is addressed to 500 users, the Internet Mail Service will
  process the first 250 recipients in the RCPT TO commands.

- It will then transmit the message data in a DATA command.

- After the data is finished, the Internet Mail Service will process the final
  250 recipients in the RCPT TO commands.

- The message data is sent again in the DATA command.

NOTE: Using this registry entry may have an adverse effect on the performance of
high volume Exchange Server Internet Mail Service computers because a message
may be transmitted multiple times. Typically, this registry entry is most useful
when you need to work around the limitations set on the SMTP host to which the
Internet Mail Service is sending mail.

Additional query words: xfor, xims, restrict, unix

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Keywords          :  
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : WINNT:5.5

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