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
@@ -682,8 +682,13 @@
       if ($config_inline || $config_attach) {
         $body_limit = PhabricatorEnv::getEnvConfig('metamta.email-body-limit');
 
-        $patch = $this->buildPatchForMail($diff);
-        if ($config_inline) {
+        try {
+          $patch = $this->buildPatchForMail($diff, $body_limit);
+        } catch (ArcanistDiffByteSizeException $ex) {
+          $patch = null;
+        }
+
+        if (($patch !== null) && $config_inline) {
           $lines = substr_count($patch, "\n");
           $bytes = strlen($patch);
 
@@ -706,7 +711,7 @@
           }
         }
 
-        if ($config_attach) {
+        if (($patch !== null) && $config_attach) {
           // See T12033, T11767, and PHI55. This is a crude fix to stop the
           // major concrete problems that lackluster email size limits cause.
           if (strlen($patch) < $body_limit) {
@@ -1411,13 +1416,14 @@
       array('style' => 'font-family: monospace;'), $patch);
   }
 
-  private function buildPatchForMail(DifferentialDiff $diff) {
+  private function buildPatchForMail(DifferentialDiff $diff, $byte_limit) {
     $format = PhabricatorEnv::getEnvConfig('metamta.differential.patch-format');
 
     return id(new DifferentialRawDiffRenderer())
       ->setViewer($this->getActor())
       ->setFormat($format)
       ->setChangesets($diff->getChangesets())
+      ->setByteLimit($byte_limit)
       ->buildPatch();
   }
 
diff --git a/src/applications/differential/render/DifferentialRawDiffRenderer.php b/src/applications/differential/render/DifferentialRawDiffRenderer.php
--- a/src/applications/differential/render/DifferentialRawDiffRenderer.php
+++ b/src/applications/differential/render/DifferentialRawDiffRenderer.php
@@ -5,6 +5,7 @@
   private $changesets;
   private $format = 'unified';
   private $viewer;
+  private $byteLimit;
 
   public function setFormat($format) {
     $this->format = $format;
@@ -35,6 +36,15 @@
     return $this->viewer;
   }
 
+  public function setByteLimit($byte_limit) {
+    $this->byteLimit = $byte_limit;
+    return $this;
+  }
+
+  public function getByteLimit() {
+    return $this->byteLimit;
+  }
+
   public function buildPatch() {
     $diff = new DifferentialDiff();
     $diff->attachChangesets($this->getChangesets());
@@ -52,15 +62,18 @@
     $bundle = ArcanistBundle::newFromChanges($changes);
     $bundle->setLoadFileDataCallback(array($loader, 'loadFileData'));
 
+    $byte_limit = $this->getByteLimit();
+    if ($byte_limit) {
+      $bundle->setByteLimit($byte_limit);
+    }
+
     $format = $this->getFormat();
     switch ($format) {
       case 'git':
         return $bundle->toGitPatch();
-        break;
       case 'unified':
       default:
         return $bundle->toUnifiedDiff();
-        break;
     }
   }
 }