How to test to see if an smtp mail server is available using telnet
open a telnet session as follows:
telnet mailserver 25
if it responds as follows:
220 EXCH02.corp.mailserver.co.nz Microsoft ESMTP MAIL Service ready at Tue, 8 Oct 2019 17:00:30 +1300
250 EXCH02.corp.mailserver.co.nz Hello [172.16.21.10]
451 4.7.0 Timeout waiting for client input
Connection to host lost.
then everything is good.
however, if it responds:
C:\Windows\system32>telnet mailserver 25
Connecting To mailserver...Could not open connection to the host, on port 25: Connect failed
'helo' is not recognized as an internal or external command,
operable program or batch file.
there is a problem
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