>>/21249/
> doubtlessly emacs maybe with gnus 

Emacs, but with rmail. People say that he is sole user of rmail and that package bundled with emacs only because of Stallman.

He actually wrote about his computing style: https://stallman.org/stallman-computing.html
Very autistic.

Gnus is pretty bad for email, it is slow and not so good in search, also not so easy because it is NNTP reader first, not email. Something like mu4e is better.

t. gnus-for-email user