Not recommended to use in production yet. Even Beta is not really handable at all at the moment.
For more information have a look at mailpile.is.
Although mailpile.is has some more or less serious issues pending, this is the best effort to solve the 'single web mail client' to 'multiple server mail accounts' problem.
I started to create working kind of theme based styling via LESS instead of hardcoded inline values.
You can find the original source code at github.com/mailpile/Mailpile.
I forked it to my own repo at das-repo.de/web/Mailpile, so to be independent.
Docker build for the modern, fast web based email client with user-friendly encryption and privacy features.
Example run command:
docker run -d --name=mailpile -p 127.0.0.1:33411:33411 mkodockx/docker-mailpile
Example run command (exposing the storage volume):
docker run -d --name=mailpile -p 127.0.0.1:33411:33411 -v <storage location>:/root/.local/share/Mailpile mkodockx/docker-mailpile
Access Mailpile entering the url:
in your browser.