XIMS: How to Stop Spam Mail Messages from Using IMS Relay Agent

The Microsoft Exchange Server Internet Mail Service may be configured as a publicly accessible relay mail. In this configuration, the outside users can use the relay Internet Mail Service as an agent for unsolicited commercial e-mail (UCE or spam), flooding others with many copies of the same message. Spam is an attempt to force messages on people who would not otherwise choose to receive them. This article illustrates two possible workarounds for this problem.

Scenario 1

This workaround requires another Internet Mail Service to be installed and dedicated for outbound mail. Essentially, it queues all non-internal mail to a dead IP address, which, hopefully, would allow the administrators to track where these Internet messages are coming from.

1. Open the properties for the Internet Mail Service on the server accepting inbound mail.
2. On the Connections tab for the server, select the option to forward all messages to the host, and enter the IP address of a valid computer on the network that will not accept an SMTP connection (for example, 2.2.2.2, if that computer is a non-SMTP host).
3. Click the Specify by email domains button.
4. Add a domain of "sample.microsoft.com," and forward to the IP address of another Exchange Server configured for outbound SMTP message delivery.
5. Repeat steps 2 through 4 for all other inbound domains.
6. Stop and restart the Internet Mail Service.

Scenario 2

This workaround restricts the Internet Mail Service from routing mail to your hosts' IP address. This applies only if you have Exchange 5.5. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

1. Install Service Pack 1 or later for Exchange Server 5.5.
2. Select the Connections applet from the Exchange Server Administrator program, and go to the Routing property page of the Internet Mail Service.
3. Select Reroute incoming SMTP mail (required for POP3/IMAP4 support), and then select Routing Restrictions.
4. In Specify the hosts and clients that can route mail when the following conditions are met dialog box, choose your hosting option, and then click Add to specify restricted IP addresses.