הגבלת משתמשים לשליחת דואר בתוך הארגון בלבד

First we need to configure the Exchange server to check Restricting list before sending mail. To do so we need to add Registry key listed bellow at the following location: 

HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/Resvc/Parameters

Value Name: CheckConnectorRestrictions

Data Type: REG_DWORD

Radix: Hexadecimal

Value: 1

Or simply save the following lines to .reg file and import it to registry

Windows Registry Editor Version 5.00

 

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RESvc\Parameters]

"CheckConnectorRestrictions"=dword:00000001

After creating the registry key we need to create a mail-enabled group for restricted users at the Active Directory Users and Groups console.

Make sure you Mail-Enable this group.

Now create SMTP connector with regular settings accept that in Delivery Restrictions tab add the group you just created at the Reject messages from section.

To apply the changes restart the Microsoft Exchange Routing Engine and SMTP Services.

More information at:
http://www.msexchange.org/tutorials/MF009.html
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q277872