[Dovecot] How to make pops

Hi, I use dovecot (pop) with gentoo but it's not securize. I would like to use pops but i don't how to do this. I think i have to use certificates...

This my dovecot.conf : protocols = imap imaps pop3 pop3s

imap_listen = * pop3_listen = * imaps_listen = * pop3s_listen = * ssl_disable = no login = imap login = pop3 default_mail_env = maildir:%h/.maildir mbox_locks = fcntl dotlock auth = default auth_mechanisms = plain auth_userdb = passwd auth_passdb = pam dovecot auth_user = root auth_verbose = yes auth_debug = yes

Thanks for your help