There are a number of automated open relay tests available. Alternately, we can also manually perform the test for an open relay.
There are several automated open relay testers. We need to use a telnet session to access and use their services. The best-known relay tester is
To use this service, we enter the following command at the command prompt of the mail server we are testing:
An example session follows:
$ telnet relay-test.mail-abuse.org Trying 22.214.171.124... Connected to cygnus.mail-abuse.org. Escape character is '^]'. Connecting to 999.888.777.666 ... <<< 220 domain.com ESMTP My_MTA >>> HELO cygnus.mail-abuse.org <<< 250 domain.com :Relay ...