Here's a quick "how to" for anyone who has configured the GNAT Box email proxy to only accept mail addressed to your domain(s) [Authorization -> Email Proxy -> Domain(s) to Accept], and want to verify that the SMTP proxy is, in fact, rejecting spam relaying.
Telnet into your SMTP server and entering the following exchange. You may need to turn on local echo in your telnet session to see what you are typing. The responses that you will get from the GNAT Box SMTP Proxy are shown in parenthesis. The "501 Invalid domain" is the important one. If you get "250 OK" at this point, then your GNAT Box is not correctly configured to block an attempt to relay spam. Replace mail.yourdomain.com with the correct name or IP address of your mail server. The other domains and addresses may be used as shown below. The gist of what we are doing is logging into an SMTP session and attempting to send email to [EMAIL PROTECTED], which (hopefully) isn't in the domain that the GNAT Box has been configured to accept email for. telnet mail.yourdomain.com 25 (220 SMTP ready) HELO somedomain.com (250 OK) MAIL FROM: [EMAIL PROTECTED] (250 OK) RCPT TO: [EMAIL PROTECTED] (501 Invalid domain) quit Mike Burden Lynk Systems (616)532-4985 [EMAIL PROTECTED]
