Even giving them "email+their-business@gmail.com" (instead of email@gmail.com), as every single Gmail user is able to do, will no doubt sow confusion.
That's clever. But doesn't it cause friction when trying to relay the address e.g. over the phone?
> to avoid "why is my business name in your email?" questions, I rot13 it.
That's a neat idea.
> That's why I've updated my SMTP config to handle the hyphen character the same way as the plus sign over 10 years ago.