This question pertains to the Exchange 2013 environment.
We have a user internal to the organization that has sent an unsolicited e-mail to hundreds of individual addresses within (and outside) our organization. He put all addresses in the
To field. We would like to moderate such future messages in a way that when any of the
Bcc fields contain more than 50 (or 100, 200...) recipients, that the message be sent for moderation.
Is it possible to create such mail flow rule in Exchange and how?
I already know that I can limit the number of max recipients per message, but that does not fix the issue, since the user can split his message into multiple bulk emails.