https://pdos.csail.mit.edu/archive/mbox/
It's a bit more complete than this.
mbox COMMAND
$ mbox mktemp /tmp/tmp.cfJElOQmNK Sandbox Root: > /tmp/sandbox-30749 > F: /tmp/sandbox-30749/tmp/tmp.cfJElOQmNK F:/tmp/tmp.cfJElOQmNK [C]ommit all, [c]ommit, [i]gnore, [d]iff, [l]ist tree, [q]uit ?> q $ firejail --private=/path/to/home-for-command COMMAND
[0]: https://github.com/tsgates/mbox
[1]: https://firejail.wordpress.com/
https://pdos.csail.mit.edu/archive/mbox/
It's a bit more complete than this.