@gvs @delta Simplex has two options for routing messages: the centralized SMP servers, and a 2-hop onion/Tor-like private message routing using forwarding nodes. Both of these are easily blocked if you want to shutdown access to Simplex for users.

XMPP: easy to block
Anything using Nostr: easy to block

Shutting down all email services in your jurisdiction: much harder to accomplish