The new users can put a loooooooooooong mail

Hello... I have a question. What I must do if I want to put a max number of characters in a field of Community Builder (1.9).

The new users can put a loooooooooooong mail, and that could cause a damage to the site... thanks!

in field manager, open the field that you want to edit. at the bottom of the page you will see "Max length" put the number of characters that you want them to add in there and save it. Remember that it counts all characters including the @emailservername.com

Thanks a lot