Ok. So I'm in the process of upgrading all the Cisco firewalls to
IPFire. So far I've been getting compliments on how much faster the
internet is. I didn't want to brag to them about how I invented it.
It's our little secret.

An interesting problem popped up in this: One client is using a spam
filter service that forwards their email through 1 of 15 servers on a few
different networks. I'm supposed to restrict permission on inbound port
25 to these 15 addresses or to those few networks. I could do it in GWIA
but how does one do something like this in a firewall?

Scratching head and sucking Maalox makes it difficult to type.