Dear form creators,
Please stop trying to be smart asses and say an address such as firstname.lastname@example.org is not OK. As a matter of fact IT IS!
If you want to be shocked, find out that even *@some.other.fqdn.ok is ALSO OK!
And If you really want to be correct and validate addresses against some regexp, there are only some really LOOOOOONG ones which should make it clear that your itsy-bitsy regexp which pretends to match valid email addresses, IS WRONG!
Correct regexps/codes that validate email addresses look something like this or like this. So please stop te nonsense.
Reasonable email addresses can and do contain . and + along many other characters in the local part (i.e. the part before the @).
PLEASE GET THIS THROUGH YOUR THICK SKULLS: THE ONLY RELIABLE WAY TO VALIDATE THE VALIDITY OF AN EMAIL ADDRESS IS TO TRY TO SEND MAIL TO IT.