Verifies that an email is valid.

Does not grok i18n domains. Not RFC compliant.

function is_email( $email, $deprecated = false ) {
	if ( ! empty( $deprecated ) ) {
		_deprecated_argument( __FUNCTION__, '3.0.0' );
	}

	// Test for the minimum length the email can be.
	if ( strlen( $email )  count( $subs ) ) {
		/** This filter is documented in wp-includes/formatting.php */
		return apply_filters( 'is_email', false, $email, 'domain_no_periods' );
	}

	// Loop through each sub.
	foreach ( $subs as $sub ) {
		// Test for leading and trailing hyphens and whitespace.
		if ( trim( $sub, " tnrx0B-" ) !== $sub ) {
			/** This filter is documented in wp-includes/formatting.php */
			return apply_filters( 'is_email', false, $email, 'sub_hyphen_limits' );
		}

		// Test for invalid characters.
		if ( ! preg_match( '/^[a-z0-9-]+$/i', $sub ) ) {
			/** This filter is documented in wp-includes/formatting.php */
			return apply_filters( 'is_email', false, $email, 'sub_invalid_chars' );
		}
	}

	// Congratulations, your email made it!
	/** This filter is documented in wp-includes/formatting.php */
	return apply_filters( 'is_email', $email, $email, null );
}