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