Our group, our team, our department, our firm, us'ns, whatever sets apart a collection of people who want to share messages and files with one another with assured heavy duty security. A medical service. A multi-location legal office. An entire company. Whatever.
The solution to group needs is a variation of that used for professionals and their clients, as explained in the Pattern Pulverizers section. That is, every member of the group is given a flash drive in which the keys have been totally swapped out and replaced with a set that is unique to the group. They can communicate freely with each other, but no-one outside has a copy of the in-group keys.
There are strong incentives for the flash drives not to be copied or distributed outside of the group. First, it would be an essential breach of group security. Second, the underlying license is updated periodically; the update system is designed to detect usage by persons who are not on, or who have been removed from, the group's roster.
MarpX Privacy is designed to work from flash drives on computers that need not be connected to your network. Do you have Windows machines that are obsolete or nearing the end of their life cycle? Set them aside as privacy machines that anybody in the group may use, and keep those machines totally offline. More secure yet... Supply your team members flash drives to carry encrypted and decrypted content back and forth to the "privacy machines", so that the flash drives containing MarpX Privacy installations are never attached to network computers.
Does that suggestion mean that MarpX Privacy is unsafe for networks? Of course not! But as the inventor of MarpX Privacy and the writer of the C++ source code I deeply respect the security concerns of IT System Administrators. Be cautious; that's part of your job qualifications. This independent flash drive design enables your team to use effective privacy tools entirely independent of your network. Still nervous? Look up "Doug Lowry Steubenville OH" on the Internet; you will see 17 years as a Clerk of General Assembly of The Presbyterian Church in Canada followed by a dozen years as full time Professor of Business and Marketing at Franciscan University of Steubenville. I'm Doug Lowry and as inventor of MarpX Privacy, I take responsibility that copies of programs that are code signed by Marpex Inc. of Steubenville are safe.