Advanced Search: search for exact/partial username?

Since I'm planning to migrate from a single email address (user@domain.com) to your new Masked Email, it would be very helpful if I could search for entries that have the username user@domain.com (using =username:user@domain.com). And it would be even better if I could search just for the domain part (suggestion ~username:domain.com).

Would it be possible to add this?