diff --git a/src/applications/differential/editor/DifferentialTransactionEditor.php b/src/applications/differential/editor/DifferentialTransactionEditor.php
--- a/src/applications/differential/editor/DifferentialTransactionEditor.php
+++ b/src/applications/differential/editor/DifferentialTransactionEditor.php
@@ -766,10 +766,14 @@
         }
 
         if ($config_attach) {
-          $name = pht('D%s.%s.patch', $object->getID(), $diff->getID());
-          $mime_type = 'text/x-patch; charset=utf-8';
-          $body->addAttachment(
-            new PhabricatorMetaMTAAttachment($patch, $name, $mime_type));
+          // See T12033, T11767, and PHI55. This is a crude fix to stop the
+          // major concrete problems that lackluster email size limits cause.
+          if (strlen($patch) < $body_limit) {
+            $name = pht('D%s.%s.patch', $object->getID(), $diff->getID());
+            $mime_type = 'text/x-patch; charset=utf-8';
+            $body->addAttachment(
+              new PhabricatorMetaMTAAttachment($patch, $name, $mime_type));
+          }
         }
       }
     }