Not sure if this is at possible.
Got a client asking if there’s a way to block incoming emails that are sent to multiple accounts on their domain. They are having space issues cause their clients send the same email with multiple attachments to 3 accounts on our domain. IMO they should just talk to their clients instead and train them out of bad habits.
Anyway, their idea, lets say they have an address to receive documents with case numbers. They assign 1 account to be able to receive all cases an all other accounts that are sent the same email are automatically blocked. If that first part is possible then also sender receives and automatic reply that their mail was blocked.