SMG: Block spoof sender using custom rule

I thought it would be good to share this, it's a workaround that I've created some time ago

Back story: In normal circumstances, no sender from own domain is expected from external

                   (Internet)

                  Emails from own domain should go internally between exchange and not outside

                   MTA/source.


                e.g  

                 Fake sender example.com (Internet) ---> SMG ---> Exchange ---> Mailbox (example.com)


                 Mailbox (example.com) ---> Exchange ---> Mailbox (example.com)Objective: Block spoofed sender


Solution: We may use SMG content filtering