Set explicit Message-ID in EmailMultifactorMethod::sendEmail()

diff --git a/wcfsetup/install/files/lib/system/user/multifactor/EmailMultifactorMethod.class.php b/wcfsetup/install/files/lib/system/user/multifactor/EmailMultifactorMethod.class.php
index f40b57bf6f6418c77b8f47243fa2605718ec1db0..cde537e50cba992fa83d33cfabe8dc4547789c85 100644 (file)
--- a/wcfsetup/install/files/lib/system/user/multifactor/EmailMultifactorMethod.class.php
+++ b/wcfsetup/install/files/lib/system/user/multifactor/EmailMultifactorMethod.class.php
@@ -110,6 +110,12 @@ final class EmailMultifactorMethod implements IMultifactorMethod
     {
         $email = new SimpleEmail();
         $email->setRecipient($setup->getUser());
+        $email->setMessageID(\sprintf(
+            'com.woltlab.wcf.multifactor.email/%d/%d/%s',
+            $setup->getUser()->userID,
+            TIME_NOW,
+            \bin2hex(\random_bytes(8))
+        ));
 
         $email->setSubject(
             WCF::getLanguage()->getDynamicVariable('wcf.user.security.multifactor.email.subject', [