I tried to register users using Simple Users with their email as username but I receive an invalid username error. I assume this is because of the @ symbol because when I replace it with an _ it works. So when the user later tries to log in using their email, I simply do the same thing. The whole process is invisible to the user.
So my question is, does anyone else have any experience with this? Is automatically replacing the @ symbol with an underscore the best way? Can you think of any reasons this is a bad idea? What other characters are supported as part of an email address but not as part of a username? Am I simply going to have to trial and error these? I couldn't find anything about it in the documentation.