Allows the characters that are allowed in an email address.
Allows characters A-Z, a.z, 0-9, @, . (dot), !, #, $, %, &, ', *, +, -, /, =, ?, ^, _, `, {, |, }, and ~.
Only one @ is allowed in the string and more than one dot in a row are not allowed. Note that the character validation does not validate the entire string as being a valid email address since it only does validation on a per-character level, resulting in the typed character either being added to the string or not.