I'm imagining a "War Games" scenario of blocking inbound mail and rerouting outbound mail.
Blocking Yahoo, AOL, QQ, SendGrid... Sending via AWS.
Blocking AWS, OVH, Google, Chinamobile... Sending via ProofPoint.
Blocking ProofPoint, China, Thailand, India, Russia, France, Brazil, USA, Egypt, Vietnam... Sending via Germany.
Blocking 0.0.0.0/0 0::0/0. Sending via \0
Error: The only winning move is not to play.
Would you like a carrier pigeon?