Use netstat to confirm you're only listening on the imaps port, and not the plain imap port. Then reconfigure your account settings in Thunderbird to use SSL/TLS connection security with your IMAP server. You'll get a warning because you're using a self-signed certificate, authorise the exception.

If you got to this point and everything worked (and you understand what you've done) - congratulations, you have set up a working email server and you can now have an intelligent conversation with an employer about this hugely important system.