diff --git a/src/applications/metamta/management/PhabricatorMailManagementShowInboundWorkflow.php b/src/applications/metamta/management/PhabricatorMailManagementShowInboundWorkflow.php
index 5226bd2dc2..ea2bf197dd 100644
--- a/src/applications/metamta/management/PhabricatorMailManagementShowInboundWorkflow.php
+++ b/src/applications/metamta/management/PhabricatorMailManagementShowInboundWorkflow.php
@@ -63,6 +63,9 @@ final class PhabricatorMailManagementShowInboundWorkflow
       $info[] = null;
       $info[] = pht('HEADERS');
       foreach ($message->getHeaders() as $key => $value) {
+        if (is_array($value)) {
+          $value = implode("\n", $value);
+        }
         $info[] = pht('%s: %s', $key, $value);
       }
 
diff --git a/src/applications/metamta/receiver/PhabricatorObjectMailReceiver.php b/src/applications/metamta/receiver/PhabricatorObjectMailReceiver.php
index 9202e710f5..8c88e4e1f5 100644
--- a/src/applications/metamta/receiver/PhabricatorObjectMailReceiver.php
+++ b/src/applications/metamta/receiver/PhabricatorObjectMailReceiver.php
@@ -156,7 +156,7 @@ abstract class PhabricatorObjectMailReceiver extends PhabricatorMailReceiver {
         '(?P<sender>\w+)'.
         '\\+'.
         '(?P<hash>[a-f0-9]{16})'.
-      '$)U';
+      '$)Ui';
 
     return $regexp;
   }
@@ -166,7 +166,9 @@ abstract class PhabricatorObjectMailReceiver extends PhabricatorMailReceiver {
     PhabricatorUser $sender) {
     $parts = $this->matchObjectAddressInMail($mail);
 
-    return $this->loadObject($parts['pattern'], $sender);
+    return $this->loadObject(
+      phutil_utf8_strtoupper($parts['pattern']),
+      $sender);
   }
 
   public static function computeMailHash($mail_key, $phid) {