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How to lock down an SMTP relay to prevent spam in Exchange Server 2003

Learn how to configure SMTP relay restrictions on Exchange Server 2003 to prevent spam while maintaining email flow between Exchange Server and your ISP.

We're running Exchange Server 2003, and we've been having a problem with spammers relaying email through our default SMTP virtual server. Can you please give me a step-by-step procedure for locking down the open relay while still maintaining email flow between the Exchange Server organization and our Internet Service Provider (ISP)?

Exchange Server 2003 is a "closed relay" by default. This means that unless your usernames and passwords are compromised, an unauthenticated computer (SMTP host) cannot relay messages. It may be possible that the default SMTP relay restrictions were removed; in which case, you will want to re-enable them.

Microsoft details the procedure for configuring SMTP relay settings on Exchange Server 2003 on its website. All of your Exchange servers will be able to continue to send outbound email because they are authenticated computers.

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