_:n29aa153e314243d4bed9ac72351d79f1xb2
<http://schema.org/text>
"SMTP communicates over port 25.  We will now try to use TELNET to connect to their mail server \"mail.theirdomain.com\"\n\n* Open a CMD prompt\n* TELNET MAIL.THEIRDOMAIN.COM 25\n\nYou should see something like this as a response:\n220 mx.google.com ESMTP 6si6253627yxg.6\n\nBe aware that different servers will come up with different greetings but you should get SOMETHING.  If nothing comes up at this point there are 2 possible problems.  Port 25 is being blocked at your firewall, or their server is not responding.  Try a different domain, if that works then it's not you.\n\n"
<https://frontend.spiceworks.com/how_to/11-test-email-flow-using-smtp-commands?from_group=240>