Fatal “Class ‘Normalizer’ not found” on the Posts and Pages screens with the Gmail mailer and All in One SEO

// WP Mail SMTP 4.10.0: stop the "Class 'Normalizer' not found" fatal on hosts without PHP intl.

// Remove once the plugin update with the fix is installed, or once intl is enabled.

if ( ! extension_loaded( 'intl' ) && ! class_exists( 'Normalizer', false ) ) {

	class Normalizer {

		const FORM_D  = 4;

		const FORM_KD = 8;

		const FORM_C  = 16;

		const FORM_KC = 32;

		const NFD     = 4;

		const NFKD    = 8;

		const NFC     = 16;

		const NFKC    = 32;

		public static function isNormalized( $string, $form = self::FORM_C ) {

			return true;

		}

		public static function normalize( $string, $form = self::FORM_C ) {

			return $string;

		}

	}

}