How to Determine whether the Exchange Server is an open SMTP relay

From a remote wortstaion, follow these steps:

1. Click Start, click Run, type telnet, and then click OK.

2. At the Telnet command prompt, type set local_echo, and then press ENTER.

3. At the Telnet command prompt, type open Exchange-IP-address 25, and then press ENTER (where Exchange-IP-address is the external public IP address of the Small Business Server computer).
The output is similar to the following:

220 mail.chicagotech.local Microsoft ESMTP MAIL Service, Version: 5.0.2195.4905 ready at "date" -0500

4. Type ehlo anydomain.com, and then press ENTER (where anydomain should not be the Exchange Server computer's e-mail domain. Make sure that the last line is:

250 OK

5. Type mail from:username@anydomain.com, and then press ENTER (where username@anydomain is an SMTP address that is not hosted on the Exchange Server computer). Make sure that the result is:

250 2.1.0 username@anydomain.com....Sender OK

6. Type rcpt to:user@spam.com, and then press ENTER (where user@spam is not your e-mail domain). Make sure that the result is one of the following two responses:

550 5.7.1 Unable to relay for user@spam.com
-or-
250 2.1.5 user@spam.com

7. If the result is "550 5.7.1 Unable to relay for user@spam.com," the Exchange server is not an open SMTP relay.

8. If the result is "250 2.1.5 user@spam.com," the Exchange server is an open SMTP relay.

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