How to force use of TLS/SSL

[Torbjorn Astlind]

Hello,
I want to open up for users external to our domain to use Eudora 5.1
only with POP-TLS/SSL. I do not want to open up for nonencrypted
POP. All popusers use APOP from within the domain.
Please can someone give me a hint how to achive this.
Do I have to use alternat port and a firewall filter to pass the
alternate port only?
Thanks for any help and advice,
Torbj�rn