Ticket #50720: 50720-3.patch

src/wp-includes/pluggable.php

@@ -216 +216 @@
                         require_once ABSPATH . WPINC . '/PHPMailer/SMTP.php';
                         require_once ABSPATH . WPINC . '/PHPMailer/Exception.php';
                         $phpmailer = new PHPMailer\PHPMailer\PHPMailer( true );
+
+                        /**
+                         * Set email validation to use WordPress's built-in is_email().
+                         * @ticket 50720
+                         */
+                        $phpmailer::$validator = 'is_email';
                 }
 
                 // Headers.