Para uma validação mais consistente utilze expressões regulares. Um ótimo exemplo de validação do framework Kohana: public static function email($email, $strict = FALSE)
{
if (UTF8::strlen($email) > 254)
{
return FALSE;
}
if ($strict === TRUE)
{
$qtext = '[^\\x0d\\x22\\x5c\\x80-\\xff]';
$dtext = '[^\\x0d\\x5b-\\x5d\\x80-\\xff]';
$atom = '[^\\x00-\\x20\\x22\\x28\\x29\\x2c\\x2e\\x3a-\\x3c\\x3e\\x40\\x5b-\\x5d\\x7f-\\xff]+';
$pair = '\\x5c[\\x00-\\x7f]';
$domain_literal = "\\x5b($dtext|$pair)*\\x5d";
$quoted_string = "\\x22($qtext|$pair)*\\x22";
$sub_domain = "($atom|$domain_literal)";
$word = "($atom|$quoted_string)";
$domain = "$sub_domain(\\x2e$sub_domain)*";
$local_part = "$word(\\x2e$word)*";
$expression = "/^$local_part\\x40$domain$/D";
}
else
{
$expression = '/^[-_a-z0-9\'+*$^&%=~!?{}]++(?:\.[-_a-z0-9\'+*$^&%=~!?{}]+)*+@(?:(?![-.])[-a-z0-9.]+(?<![-.])\.[a-z]{2,6}|\d{1,3}(?:\.\d{1,3}){3})$/iD';
}
return (bool) preg_match($expression, (string) $email);
} Um abraço.