Most people use the same email address everywhere. One breach and it leaks for years. The known fix is a different alias per service — but every tool I tried made me create each alias upfront . I wanted the opposite: a subdomain where every address just works, and the alias is born the moment the first email arrives. This post is the engineering behind that: how to run a catch-all subdomain mail flow without becoming an open relay, and how to forward mail without nuking your delive...