How to test if SMTP email gateway or server is accepting or relaying your emails successfully using commandline option through telnet from Unix or Windows platforms. telnet emailgateway.example.com smtp 220 emailgateway.example.com ESMTP Postfix EHLO localhost 250-emailgateway.example.com 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250 8BITMIME MAIL FROM: <testadmin@example1.com> 250 Ok RCPT TO: <unknown@unknowndomain.com> 554 <unknown@unknowndomain.com>: Relay access denied RCPT TO: <unknown@example1.com> 554 <unknown@example.com>: Relay access denied RCPT TO: <user1@example1.com> 250 Ok DATA 354 End data with <CR><LF>.<CR><LF> Subject: test test 1 2 3 . 250 Ok: queued as 5152A39097 QUIT 221 Bye
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