@sahil I don't recommend self-hosting email now either.
But I question using Nginx Proxy Manager when Nginx itself is easy to learn. Especially for a single app.
And I question using Docker compose when your virtual machine is literally hosting just one app.
When I help people on the #GhostBlog forums, nearly all questions come from people with these more complex setups, not the officially supported simple "wizard" which helps you interactively configure the app, setup Nginx, SSL and systemd