diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -3448,6 +3448,20 @@
     array $email_cc,
     array $unexpandable) {
 
+    // Remove disabled user accounts from CC recipients - T16033
+    if ($email_cc) {
+      $cc_map = id(new PhabricatorPeopleQuery())
+        ->setViewer(PhabricatorUser::getOmnipotentUser())
+        ->withPHIDs($email_cc)
+        ->withIsDisabled(true)
+        ->execute();
+      foreach ($cc_map as $cc_recipient) {
+        if ($cc_recipient->getIsDisabled()) {
+          unset($email_cc[$cc_recipient->getPHID()]);
+        }
+      }
+    }
+
     $targets = $this->buildReplyHandler($object)
       ->setUnexpandablePHIDs($unexpandable)
       ->getMailTargets($email_to, $email_cc);