diff --git a/src/applications/metamta/adapter/phpmailerlite/PhabricatorMailImplementationPHPMailerLiteAdapter.php b/src/applications/metamta/adapter/phpmailerlite/PhabricatorMailImplementationPHPMailerLiteAdapter.php
index 822ee8e32e..af131b28fb 100644
--- a/src/applications/metamta/adapter/phpmailerlite/PhabricatorMailImplementationPHPMailerLiteAdapter.php
+++ b/src/applications/metamta/adapter/phpmailerlite/PhabricatorMailImplementationPHPMailerLiteAdapter.php
@@ -51,7 +51,11 @@ class PhabricatorMailImplementationPHPMailerLiteAdapter
   }
 
   public function addHeader($header_name, $header_value) {
-    $this->mailer->AddCustomHeader($header_name.': '.$header_value);
+    if (strtolower($header_name) == 'message-id') {
+      $this->mailer->MessageID = $header_value;
+    } else {
+      $this->mailer->AddCustomHeader($header_name.': '.$header_value);
+    }
     return $this;
   }