That's not really my use case, but seems like an important concern for many! At that point, you probably want to use whatever features one of the big providers

That's not really my use case, but seems like an important concern for many! At that point, you probably want to use whatever features one of the big providers use, like: https://proton.me/support/aliases-mail https://proton.me/support/aliases-mail Maybe even something that'd sit in front of a mail server that you yourself control, I wonder what the variety of options out there is.