Two concerns: What about 33Mail? Is this not the same thing with the tag shifted? What if this becomes popular? Spammers can write a special case for @mailher

Two concerns: What about 33Mail? Is this not the same thing with the tag shifted? What if this becomes popular? Spammers can write a special case for @mailhero.io addresses that strips or changes the prefix. If you block those avenues, it just turns into a much easier password guessing game: the user has dozens of passwords, and they're all one common word, lowercase.