diff --git a/src/applications/metamta/controller/PhabricatorMetaMTAReceiveController.php b/src/applications/metamta/controller/PhabricatorMetaMTAReceiveController.php
index 6afb4b3c17..2ae211e2ad 100644
--- a/src/applications/metamta/controller/PhabricatorMetaMTAReceiveController.php
+++ b/src/applications/metamta/controller/PhabricatorMetaMTAReceiveController.php
@@ -28,6 +28,12 @@ final class PhabricatorMetaMTAReceiveController
         array(
           'text' => $request->getStr('body'),
         ));
+
+      // Make up some unique value, since this column isn't nullable.
+      $received->setMessageIDHash(
+        PhabricatorHash::digestForIndex(
+          Filesystem::readRandomBytes(12)));
+
       $received->save();
 
       $received->processReceivedMail();
diff --git a/src/applications/metamta/controller/PhabricatorMetaMTASendGridReceiveController.php b/src/applications/metamta/controller/PhabricatorMetaMTASendGridReceiveController.php
index 4b81a3c08b..fbd86a2871 100644
--- a/src/applications/metamta/controller/PhabricatorMetaMTASendGridReceiveController.php
+++ b/src/applications/metamta/controller/PhabricatorMetaMTASendGridReceiveController.php
@@ -39,6 +39,8 @@ final class PhabricatorMetaMTASendGridReceiveController
       'text' => $request->getStr('text'),
       'html' => $request->getStr('from'),
     ));
+    $received->setMessageIDHash(
+      PhabricatorHash::digestForIndex($received->getMessageID()));
 
     $file_phids = array();
     foreach ($_FILES as $file_raw) {