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RestrictExtRecips for Microsoft Exchange Server 2010

Updated: 26-February-2018
See also: RestrictExtRecips for Microsoft Exchange 2013/2016


In Exchange 2010 you can use the EAC or Shell to restrict the number of recipients per message for a mailbox.
There is no way to limit the number of external recipients a certain group of people can send to.

RestrictExtRecips application solves this problem.

You can create the following rule: if is a member of a group RestrictExternal, he cannot set more than 5 external recipients in his message. If he places 6 or more external addresses his message will not be delivered and he will get a non-delivery report message: "Too many external recipients".

The application is a custom transport agent.

Current version:


On your Exchange 2010 Hub Transport server computer:

  1. Select (or create) a user account that is a member of the local Administrators and Domain Users security group.
  2. Log on as that user.
  3. Create C:\Program Files\IvaSoft\RestrictExtRecips\ directory and download there archive file.
  4. Right-click and select 'Properties'. If there is 'Unblock' button, hit it.

    RestrictExtRecips 2010 installation Picture 1

  5. Extract all files from the zip archive to C:\Program Files\IvaSoft\RestrictExtRecips directory.
  6. Run RestrictExtRecipsSetup.exe. Click Install button. Make sure that RestrictExtRecips is appeared in the list of Transport agents. Click Enable button. Make sure that "Running" mark is in the status line.
  7. Click "Browse" button near the "NDR Template:" field. Select "C:\Program Files\IvaSoft\RestrictExtRecips\RejectedEN.eml".
  8. Click Exit button to close the program.

    RestrictExtRecips 2010 installation Picture 2


  1. Run RouteBySenderSetup.exe. Click "Add" button [1]. "RestrictExtRecips setup - Add New rule" window will appear. Select a group and set maximal number of external recipients.

    RestrictExtRecips 2010 testing Picture 1

  2. Create a test message from any member of the group used on step #1 where amount of external recipients is greater than set in the rule. Send the message. Make sure that the message is not delivered. Also make sure that you have received a non-delivery report message, like this:

    RestrictExtRecips 2010 testing Picture 2


Run RestrictExtRecipsSetup.exe. Click Uninstall button. Make sure that RestrictExtRecips is not in the list of Transport agents. Click Exit button to close the program.

About this demo version.

RestrictExtRecips demo version places "[RestrictExtRecips DEMO]" to the Subject line of each non-delivery report message it generates.


Q. I am having trouble getting the program to work. When I enable the transport agent, I get 1052 and 16023 errors in Event Viewer and the Transport service will not stay running.
A. Make sure that you have placed the software files to C:\Program Files\IvaSoft\RestrictExtRecips folder. Also note that Exchange server uses the Network Service account for the Transport Service credentials and it seems this account didn't get security permissions to RestrictExtRecips folder. Try to add Network Service account read permissions to that folder.

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