[Exim] Offtopic Q: access to exim through firewall...

Hi folks,

I would like to enable my parents to use my mail server as their 'pop box',
rather than go via their isp. I know the usual answer is to set up a pop3
server and go, but I'm worried about security and firewalls.

I have:
Exim v4, Cyrus imapd v2, a static-ip over ADSL, a Linux 2.4 firewall.
The firewall currently allows SMTP, HTTP & SSH access and not much else.

They have:
Windows XP Home using Eudora 5 over dialup.


Any thoughts on how to enable access?

Thanks,

Ruth