This is mainly used for troubleshooting POP3 connections, to check if the connection/server/password actually works. Also possible to read emails that way, but very ~1995ish. If you really, really want to (re-) experience that experience, check out alpine, the sucessor of pine.

Start connection with OpenSSL:

openssl s_client -connect yourusername.yourmailserver:995

This is non-quiet, resulting in a lot of talkback, most importantly:

    ...
    Start Time: 1693034257
    Timeout   : 7200 (sec)
    Verify return code: 0 (ok)
    Extended master secret: no
    Max Early Data: 0
---
read R BLOCK
+OK Dovecot ready.

+OK Dovecot ready. tells use the mail programme - in this case Dovecot - is ready, waiting for user & password input.

user youremailaddress
+OK
pass yourpassword
+OK Logged in.

The stat command tells you how many message, and how large they are.

stat
+OK 2 9394

Ok, two message, totalling 9394 bytes. To read it, use the retrive command, specifiying the number of the message you want to read.

retr 1

This will display the whole message, including any and all headers.