Also, the ‘@’ must not be the first character of the email address, and the last dot must at least be one character after the ‘@’ sign.
Most email validation checks assumes that the top level domain can have up to 4 characters. You have just validated the format – not its existence.
The only way to truly validate the email address is to send an email to that address and request the user to confirm by clicking on a unique link (or entering a confirmation code)Remember, if the user’s intention is to enter an invalid email address, she can do it so easily whether you have the most tough validation or not.
\d|2[0-4]\d|25[0-5])\]))$ Of course that's lacking some sanity checks and won't do domain verification (that has to be done server side) - but it should give you a pretty solid JS email format verifier.
Validating email is a very important point while validating an HTML form.