Check secure services with(out) telnet

Back in the good ole days, you could use your telnet client (or netcat) to check most services. For example, a mail account via POP3:

$ telnet pop.mailserver.tld 110
+OK [...]
user username
+OK [...]
pass yourpassword
+OK [...]

Today many servers require a secure connection, so that your data (including username and password!) won’t be readable by anyone snooping your connection. It’s a good security policy, but telnet is not able to speak to secure services. You should use Openssl instead:

$ openssl s_client -connect pop.mailserver.tld:995
+OK [...]
user username

It also works on different services, for example HTTP:

$ openssl s_client -connect
GET / HTTP/1.0

HTTP/1.0 302 Found

Using this command you can easily check and debug your secure POP, IMAP, HTTP services.


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