IMAP is blocked in some regions

[ian]

Maybe there’s a typo in there somewhere, but it’s not possible to selectively block HTTPS use in general (other than via IP-based whitelisting).

The best you could do is to host VPN and other tunnels for those in need. See the relevant comments here:

Web client possible?

Some of the topics and posts are already sparsely or transitively linked, but let me list here together all posts related to shipping static web client apps (WebAssembly, wasm, Emscripten, Rust, TCP/IP, proxy, gateway, compile, WebSocket, JMAP, JavaScript, API):