Pro 3 and Mailwasher Pro 6

When I try to Check Mail in Mailwasher Pro 6, I am unable to connect to the relevant POP3 server. I have established that this is because the firewall is blocking access.

Why is this happening (never was a problem in the previous version under XP) and what can be done about it?

FYI I’m running Vista Home + basic Comodo firewall.