diff --git a/conf/default.conf.php b/conf/default.conf.php
index ef8575ad0a..13230ce01b 100644
--- a/conf/default.conf.php
+++ b/conf/default.conf.php
@@ -522,6 +522,13 @@ return array(
 
   'differential.field-selector' => 'DifferentialDefaultFieldSelector',
 
+  // If you set this to true, users can "!accept" revisions via email (normally,
+  // they can take other actions but can not "!accept"). This action is disabled
+  // by default because email authentication can be configured to be very weak,
+  // and, socially, email "!accept" is kind of sketchy and implies revisions may
+  // not actually be receiving thorough review.
+  'differential.enable-email-accept' => false,
+
 
 // -- Maniphest ------------------------------------------------------------- //
 
diff --git a/src/applications/differential/replyhandler/DifferentialReplyHandler.php b/src/applications/differential/replyhandler/DifferentialReplyHandler.php
index a23b28f50e..7146b45d9f 100644
--- a/src/applications/differential/replyhandler/DifferentialReplyHandler.php
+++ b/src/applications/differential/replyhandler/DifferentialReplyHandler.php
@@ -88,7 +88,7 @@ class DifferentialReplyHandler extends PhabricatorMailReplyHandler {
   }
 
   public function getSupportedCommands() {
-    return array(
+    $actions = array(
       DifferentialAction::ACTION_COMMENT,
       DifferentialAction::ACTION_REJECT,
       DifferentialAction::ACTION_ABANDON,
@@ -97,6 +97,12 @@ class DifferentialReplyHandler extends PhabricatorMailReplyHandler {
       DifferentialAction::ACTION_RETHINK,
       'unsubscribe',
     );
+
+    if (PhabricatorEnv::getEnvConfig('differential.enable-email-accept')) {
+      $actions[] = DifferentialAction::ACTION_ACCEPT;
+    }
+
+    return $actions;
   }
 
   public function receiveEmail(PhabricatorMetaMTAReceivedMail $mail) {