I was asked to set up a forward on incoming emails from specific senders on a shared mailbox. We have a hybrid setup and the shared mailbox resides on-premise but the MX record for that domain is already pointing towards Exchange Online Protection.
Incoming emails from 1897 domains and 1581 individual addresses should be forwarded from the shared mailbox to another shared mailbox in the same domain which also resides on-premise , what is the most efficient approach? Do I create a bunch of rules in the on-premise Exchange or do I create them directly in Exchange Online?
Due to the sheer number of domains/users that need to be forwarded, efficiency is key.