I have a network split into two parts - one for office and server computers, and one for computers that manage scientific instruments. The instrument computers are running on the vendor's patch schedule, meaning some of them were just upgraded from windows XP, so we keep them relatively isolated from the office machines.

This has worked relatively well, but some of the instrument machines need to be able to send email via our server running postfix. I've been able to get them sending the mail by setting `mynetworks_style` to `class`, and opening up our whole block to send email. I'd like to get it so that all application servers, desktops, etc in the office subnet can still use the server to send mail, but a whitelist on the instrument subnet can send mail. Can that be configured through `mynetworks`, or does it require more configuration?