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In the olden days, we did for example telnet mailserver 110, and then we could get the combination of username/password or other checks.
With all being TLS/SSL, here is a way to do the way but with a TLS underlay.

openssl s_client -connect www.google.com:443

This enables me to :
1) show the cert ( usefull when debugging the installation of certs)
2) test to get a page GET https://www.google.com/ but the page has encryption. (same goes for LDAP/SSL and so on … )

For SMTP
openssl s_client -connect mail.google.com:25 -starttls smtp

On Windows either you install openssl
Or what I do, is I installed an Ubuntu under Windows natively
https://tutorials.ubuntu.com/tutorial/tutorial-ubuntu-on-windows#0
This enables me to use the powerfull tools of Ubuntu/python and so on, under my Windows 10 machine/environement.

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