On occasion, you might want to prevent users from sending SMTP mail to a specific external address. For instance, perhaps your company wants to restrict employees from sending messages to certain mail lists or to a competitor's employment opportunities mail address.
While you can block inbound messages from specific addresses or entire domains with message filtering in the Exchange 5.5 Internet Mail Connector (IMC), there isn't a direct way to stop outbound messages from going to a specific address. However, you can work around this limitation.
Here's one way to do it:
Messages sent from your organization to the customer recipient you created in Step 1 will now return a nondelivery report similar to the following:
Your message did not reach some or all of the
Sent: 5/3/2003 8:53 AM
The following recipient(s) could not be reached:
firstname.lastname@example.org on 5/3/2003 8:53 AM
A restriction in the system prevented delivery of the message.
You can also use these procedures to allow or prevent any employees from sending to any SMTP address: Add more users in the Accept Messages From pane in Step 3, or select Reject Messages From and add users there.
The ability to add or remove users in Step 3 gives you a lot of flexibility in selecting who can send mail to a selected external SMTP address.