We are basically doing what #signal and in particular moxie refused to do or declares impossible: federation.

Both #email and #activitypub ecosystems are all about federation.

However, #deltachat is vertically centralized in that all UIs use the same #rust core which implements all networking, encryption, chat/group/message logic in a single centralized place. The now 40+ #chatmail mail relay network is driven from centralized code.

At each level replication and federation is built in.