Open Relay Test
What is an open relay?
An open relay is a smtp server configured in such a way that is allows a third party to relay (send / receive email messages that are neither from nor for local users). Therefore, such servers are usually targets for spam senders.
How to test if your mail server is open relay
Enter the IP address of your mail server and click the "Test" button below to see if it is an open relay.
http://www.mailradar.com/openrelay/
MANUAL TESTING
To manually test your mail server you can perform the following!
Open a command prompt (start>run>cmd)
Type "telnet [your mail server IP] 25" - - - this will open an SMTP connection
Type "helo yourdomain.com" - - - server will respond "220 mx.mydom.com SMTP"
Type "mail from:" - - - server responds "250 Address Ok"
Type "rcpt to:" - - - server responds "550 not local host someotherdomain.com, not a gateway"
The reply “not a gateway” indicates the server does not allow relaying **server responses may vary depending on server type and setup
Enjoy folks..!