[21sys]

me too, but more and more relays enforce tls or startssl (which is good!) and that's where telnet isn't a good fit imho.

I came across curl when I tested the mailgun.com smtp relay (mandatory tls + auth) and it worked immediately.

[mmh0000]

If you really want to do things manually, like telnet but with ssl, see OpenSSLs sclient:

  openssl s_client -connect my.mailserver.com:465