Temorarily hold email with too many recipients and warn sender
As an Exchange online admin (or any other mail system admin for that matter) it would be nice if one could enable some kind of automated process where a user is warned about emails with too many recipients.
We've all received those annoying (or possibly damaging) emails send to dozens of people whose email addresses become unnecessarily exposed to everyone else. In many cases the email is for a legitimate purpose, and we know the sender should rather have BCCed everyone, or sent individual emails, or something.
Is there a way in Exchange Online to enable a temporary hold on an email with more than a certain number of direct or copied recipients and issue a warning to the sender that gives them the opportunity to reconsider before releasing the email? First prize would be a setting somewhere, second prize would be some kind of roll-your-own rule or script.