diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -3899,6 +3899,7 @@
     'PhabricatorPeopleTransactionQuery' => 'applications/people/query/PhabricatorPeopleTransactionQuery.php',
     'PhabricatorPeopleUserFunctionDatasource' => 'applications/people/typeahead/PhabricatorPeopleUserFunctionDatasource.php',
     'PhabricatorPeopleUserPHIDType' => 'applications/people/phid/PhabricatorPeopleUserPHIDType.php',
+    'PhabricatorPeopleUsernameMailEngine' => 'applications/people/mail/PhabricatorPeopleUsernameMailEngine.php',
     'PhabricatorPeopleWelcomeController' => 'applications/people/controller/PhabricatorPeopleWelcomeController.php',
     'PhabricatorPeopleWelcomeMailEngine' => 'applications/people/mail/PhabricatorPeopleWelcomeMailEngine.php',
     'PhabricatorPhabricatorAuthProvider' => 'applications/auth/provider/PhabricatorPhabricatorAuthProvider.php',
@@ -9895,6 +9896,7 @@
     'PhabricatorPeopleTransactionQuery' => 'PhabricatorApplicationTransactionQuery',
     'PhabricatorPeopleUserFunctionDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
     'PhabricatorPeopleUserPHIDType' => 'PhabricatorPHIDType',
+    'PhabricatorPeopleUsernameMailEngine' => 'PhabricatorPeopleMailEngine',
     'PhabricatorPeopleWelcomeController' => 'PhabricatorPeopleController',
     'PhabricatorPeopleWelcomeMailEngine' => 'PhabricatorPeopleMailEngine',
     'PhabricatorPhabricatorAuthProvider' => 'PhabricatorOAuth2AuthProvider',
diff --git a/src/applications/people/mail/PhabricatorPeopleUsernameMailEngine.php b/src/applications/people/mail/PhabricatorPeopleUsernameMailEngine.php
new file mode 100644
--- /dev/null
+++ b/src/applications/people/mail/PhabricatorPeopleUsernameMailEngine.php
@@ -0,0 +1,60 @@
+<?php
+
+final class PhabricatorPeopleUsernameMailEngine
+  extends PhabricatorPeopleMailEngine {
+
+  private $oldUsername;
+  private $newUsername;
+
+  public function setNewUsername($new_username) {
+    $this->newUsername = $new_username;
+    return $this;
+  }
+
+  public function getNewUsername() {
+    return $this->newUsername;
+  }
+
+  public function setOldUsername($old_username) {
+    $this->oldUsername = $old_username;
+    return $this;
+  }
+
+  public function getOldUsername() {
+    return $this->oldUsername;
+  }
+
+  public function validateMail() {
+    return;
+  }
+
+  protected function newMail() {
+    $sender = $this->getSender();
+    $recipient = $this->getRecipient();
+
+    $sender_username = $sender->getUsername();
+    $sender_realname = $sender->getRealName();
+
+    $old_username = $this->getOldUsername();
+    $new_username = $this->getNewUsername();
+
+    $body = sprintf(
+      "%s\n\n  %s\n  %s\n",
+      pht(
+        '%s (%s) has changed your Phabricator username.',
+        $sender_username,
+        $sender_realname),
+      pht(
+        'Old Username: %s',
+        $old_username),
+      pht(
+        'New Username: %s',
+        $new_username));
+
+    return id(new PhabricatorMetaMTAMail())
+      ->addTos(array($recipient->getPHID()))
+      ->setSubject(pht('[Phabricator] Username Changed'))
+      ->setBody($body);
+  }
+
+}
diff --git a/src/applications/people/storage/PhabricatorUser.php b/src/applications/people/storage/PhabricatorUser.php
--- a/src/applications/people/storage/PhabricatorUser.php
+++ b/src/applications/people/storage/PhabricatorUser.php
@@ -555,55 +555,6 @@
     }
   }
 
-  public function sendUsernameChangeEmail(
-    PhabricatorUser $admin,
-    $old_username) {
-
-    $admin_username = $admin->getUserName();
-    $admin_realname = $admin->getRealName();
-    $new_username = $this->getUserName();
-
-    $password_instructions = null;
-    if (PhabricatorPasswordAuthProvider::getPasswordProvider()) {
-      $engine = new PhabricatorAuthSessionEngine();
-      $uri = $engine->getOneTimeLoginURI(
-        $this,
-        null,
-        PhabricatorAuthSessionEngine::ONETIME_USERNAME);
-      $password_instructions = sprintf(
-        "%s\n\n  %s\n\n%s\n",
-        pht(
-          "If you use a password to login, you'll need to reset it ".
-          "before you can login again. You can reset your password by ".
-          "following this link:"),
-        $uri,
-        pht(
-          "And, of course, you'll need to use your new username to login ".
-          "from now on. If you use OAuth to login, nothing should change."));
-    }
-
-    $body = sprintf(
-      "%s\n\n  %s\n  %s\n\n%s",
-      pht(
-        '%s (%s) has changed your Phabricator username.',
-        $admin_username,
-        $admin_realname),
-      pht(
-        'Old Username: %s',
-        $old_username),
-      pht(
-        'New Username: %s',
-        $new_username),
-      $password_instructions);
-
-    $mail = id(new PhabricatorMetaMTAMail())
-      ->addTos(array($this->getPHID()))
-      ->setForceDelivery(true)
-      ->setSubject(pht('[Phabricator] Username Changed'))
-      ->setBody($body)
-      ->saveAndSend();
-  }
-
   public static function describeValidUsername() {
     return pht(
       'Usernames must contain only numbers, letters, period, underscore and '.
diff --git a/src/applications/people/xaction/PhabricatorUserUsernameTransaction.php b/src/applications/people/xaction/PhabricatorUserUsernameTransaction.php
--- a/src/applications/people/xaction/PhabricatorUserUsernameTransaction.php
+++ b/src/applications/people/xaction/PhabricatorUserUsernameTransaction.php
@@ -18,18 +18,27 @@
   }
 
   public function applyExternalEffects($object, $value) {
+    $actor = $this->getActor();
     $user = $object;
 
+    $old_username = $this->getOldValue();
+    $new_username = $this->getNewValue();
+
     $this->newUserLog(PhabricatorUserLog::ACTION_CHANGE_USERNAME)
-      ->setOldValue($this->getOldValue())
-      ->setNewValue($value)
+      ->setOldValue($old_username)
+      ->setNewValue($new_username)
       ->save();
 
     // The SSH key cache currently includes usernames, so dirty it. See T12554
     // for discussion.
     PhabricatorAuthSSHKeyQuery::deleteSSHKeyCache();
 
-    $user->sendUsernameChangeEmail($this->getActor(), $this->getOldValue());
+    id(new PhabricatorPeopleUsernameMailEngine())
+      ->setSender($actor)
+      ->setRecipient($object)
+      ->setOldUsername($old_username)
+      ->setNewUsername($new_username)
+      ->sendMail();
   }
 
   public function getTitle() {