They are automatic, but not just anyone can email to them. If your email address is in the organization it willr elay automatically. If it is not, then it gets flagged for approval by the admins and must be allowed into the system.
Absolutely no one has the ability to auto-email every single federal employee, that would be an absolutely gross violation of security. The systems ultimately are gatekept for that very reason and external emails must have admin approval to get relayed.