diff --git a/src/wp-includes/class-phpmailer.php b/src/wp-includes/class-phpmailer.php
index 796bd379f3..ff31db2f69 100644
--- a/src/wp-includes/class-phpmailer.php
+++ b/src/wp-includes/class-phpmailer.php
@@ -4,8 +4,16 @@
  * The PHPMailer class has been moved to the wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.
  */
 if ( function_exists( '_deprecated_file' ) ) {
-	_deprecated_file( basename( __FILE__ ), '5.5.0', WPINC . '/PHPMailer/PHPMailer.php', __( 'The PHPMailer class has been moved to wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.' ) );
+	_deprecated_file(
+		basename( __FILE__ ),
+		'5.5.0',
+		WPINC . '/PHPMailer/PHPMailer.php',
+		__( 'The PHPMailer class has been moved to wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.' )
+	);
 }
+
 require __DIR__ . '/PHPMailer/PHPMailer.php';
+require __DIR__ . '/PHPMailer/Exception.php';
 
 class_alias( PHPMailer\PHPMailer\PHPMailer::class, 'PHPMailer' );
+class_alias( PHPMailer\PHPMailer\Exception::class, 'phpmailerException' );
diff --git a/src/wp-includes/class-smtp.php b/src/wp-includes/class-smtp.php
index 28144c7125..7b93997f73 100644
--- a/src/wp-includes/class-smtp.php
+++ b/src/wp-includes/class-smtp.php
@@ -3,5 +3,13 @@
 /**
  * The SMTP class has been moved to the wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.
  */
-_deprecated_file( basename( __FILE__ ), '5.5.0', WPINC . '/PHPMailer/SMTP.php', __( 'The SMTP class has been moved to the wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.' ) );
+_deprecated_file(
+	basename( __FILE__ ),
+	'5.5.0',
+	WPINC . '/PHPMailer/SMTP.php',
+	__( 'The SMTP class has been moved to the wp-includes/PHPMailer subdirectory and now uses the PHPMailer\PHPMailer namespace.' )
+);
+
 require __DIR__ . '/PHPMailer/SMTP.php';
+
+class_alias( PHPMailer\PHPMailer\SMTP::class, 'SMTP' );