[ratg13]

Interesting and good to be aware of

When on a random CLI though my personal preference though is still to use telnet as the commands are easily memorized and there’s something more natural about typing the email out and then sending it.

[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