Restricting External mail - Exchange2000

Making an Exchange 2000 mailbox internal only, part 1

Restricting users from sending and receiving Internet mail in Exchange 5.5 is a simple task; however, enforcing these restrictions in Exchange 2000 is more complicated. Because Exchange 2000 uses SMTP as the native transport, simply deleting a user's SMTP address (to prevent receiving SMTP mail) and rejecting them in the Internet Mail Service (to prevent sending SMTP mail) is no longer an option. With some work, you can still make an Exchange 2000 mailbox internal-only.

First, create an Active Directory group for your internal-only uses. It is helpful to use a descriptive name for this group such as InternalMailOnly, which specifies its purpose. Next, make a recipient policy that creates invalid SMTP addresses (e.g., user@fake.domain.com). The users in this group will not receive external SMTP mail because of the invalid e-mail address. However, if you want to restrict users from sending Internet mail, you have more work todo. We'll discuss how this is accomplished in the next answer..... as i can input max 1930 charaters..check the part 2 ok...

Making an Exchange 2000 mailbox internal only, part 2

In part one of this tip, we described a method of restricting users from receiving external SMTP mail. Now we'll configure Exchange 2000 to prevent users from sending SMTP mail outside the organization.

In the Exchange System Manager:

Expand Routing Groups, Group Name, Connectors, and SMTP Internet connector(s).
Choose the Properties of the SMTP connector.
Choose the Delivery Restrictions tab from the Properties.
Add the group created in part one of this tip under Reject.
Do this for each SMTP connector. Although you created a delivery restriction, you still need to enable delivery restriction checking for your change to take effect. Start Regedt32.exe and perform the following registry change:

Locate and select the following registry key: HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/ Resvc/Parameters/.
Click Add Value from the Edit menu.
Add the following registry value:
Value Name: CheckConnectorRestrictions

Data Type: REG_DWORD

Radix: Hexadecimal

Value: 1

Quit the registry editor and restart the Microsoft Exchange Routing Engine and SMTP services. Now, restriction checking is enabled and the users you included in your InternalMailOnly group can only send and receive internal mail.
(Note: Be sure to back up the registry before editing it so you can restore it if something goes wrong.)