Is my sender an open relay?


Hi everyone!
I was thinking the other day - how can I exactly know if my SMTP is prone to any sort of vulnerabilities, as considerable as being an open relay?
After some digging I ran into the suggestion to use telnet IP 25. However, I am not sure if its exact purpose is to check whether the server is an open relay. When I ran it, it gave me no error, which would mean my server is an open relay.
However, when I ran a check on MXToolbox, the report said it wasn't an open relay.
So which one is correct? And, what's the best method to check on those things?
1. Check whether you running command on localhost or from the remote machine ?
if localhost then it's okie . if not then you have opened the connection from every ip .

2. Check IP restriction setting for the MTA which you are using ?
This might solve your thing .
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