diff --git a/app/controllers/accounts_controller.rb b/app/controllers/accounts_controller.rb
index a418c5f37..28313f169 100644
--- a/app/controllers/accounts_controller.rb
+++ b/app/controllers/accounts_controller.rb
@@ -141,6 +141,7 @@ class AccountsController < ApplicationController
       Register::Form.new(register_params).validate!
 
       user = Users::RegisterService.call(register_params)
+      user.mail = "#{user.login}@example.org" if user.mail.blank?
       password = register_params[:password].strip
 
       # gitea用户注册, email, username, password