Not exactly what you are asking for but many MTA's do have options to limit recipients and ways to make exceptions so there are ways to protect against this and

Not exactly what you are asking for but many MTA's do have options to limit recipients and ways to make exceptions so there are ways to protect against this and limit who can send to many people. Many enterprise mail servers have something similar to this as well. I have no idea what the military are using these days. They mention Outlook in the article so I assume they are using O365 or whatever it was renamed to. O365 has the ability to write rules based on AD group membership to limit who can mass email. Perhaps the military can temporarily take away those permissions until people have had training.