I just found: https://github.com/mail-in-a-box/mailinabox/commit/9c7d4769154cd61be80d6e4889a008126725b8e6
In which ‘@domain.mine’ would work as a catch-all, I tried it, but I’m not sure if it works yet.
Sent an email about 10 minutes ago from my work email and it has still not been received (not a bounce either though)