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function validEmail($email)
{
	$isValid = true;
	$atIndex = strrpos($email, "@");
	if (is_bool($atIndex) && !$atIndex) {
		$isValid = false;
	} else {
		$domain = substr($email, $atIndex + 1);
		$local = substr($email, 0, $atIndex);
		$localLen = strlen($local);
		$domainLen = strlen($domain);
		if ($localLen < 1 || $localLen > 64) {
			// local part length exceeded
			$isValid = false;
		} else if ($domainLen < 1 || $domainLen > 255) {
			// domain part length exceeded
			$isValid = false;
		} else if (!strrpos($domain, ".")) {
			// domain part does not have .
			$isValid = false;
		} else if ($domain[0] == '.' || $domain[$domainLen - 1] == '.') {
			// domain part starts or ends with '.'
			$isValid = false;
		} else if ($local[0] == '.' || $local[$localLen - 1] == '.') {
			// local part starts or ends with '.'
			$isValid = false;
		} else if (preg_match('/\\.\\./', $local)) {
			// local part has two consecutive dots
			$isValid = false;
		} else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain)) {
			// character not valid in domain part
			$isValid = false;
		} else if (preg_match('/\\.\\./', $domain)) {
			// domain part has two consecutive dots
			$isValid = false;
		} else if (!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/', str_replace("\\\\", "", $local))) {
			// character not valid in local part unless 
			// local part is quoted
			if (!preg_match('/^"(\\\\"|[^"])+"$/', str_replace("\\\\", "", $local))) {
				$isValid = false;
			}
		}
		/* if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A"))) {
		  // domain not found in DNS
		  $isValid = false;
		  } */
	}
	return $isValid;
}