Aug 15, 2017

How To Manually Test Your Email Server for Open Relays

From your local machine, run the following command through cmd (Windows®) or SSH (Mac and Linux):

telnet [server IP] 25
helo me
mail from: [email protected]
rcpt to:
Where [server IP] is your server's IP address.
If your relays are closed, you will receive an error that you cannot connect, similar to the following error:
Trying IP address...
Connected to
Escape character is '^]'.
550 5.7.1 relaying denied for recipient in "rcpt to:"
If you receive any other outputs, your relays are open.