Redmine

Hi All，
I am new to redmine,after installing redmine,it doesn't send email.Perhaps it's the problem of compatibility，firewall,or other unkonwn problems.What's more,it says email has sent to xxx when sending test email.
The test email log:
-------------------------------------------------------------------------
Started GET "/redmine/admin/test_email" for 192.168.20.37 at Tue Jul 24 17:11:51 +0800 2012
Processing by AdminController#test_email as HTML
Rendered mailer/test_email.text.erb within layouts/mailer (0.5ms)
Rendered mailer/test_email.html.erb within layouts/mailer (0.4ms)

Sent mail to xxx@xx.xxx (40ms)
Redirected to http://192.168.20.6/redmine/settings/edit?tab=notifications
Completed 302 Found in 102ms (ActiveRecord: 1.0ms)
---------------------------------------------------------------------------------
I don't know why:(.This is my environment.

Environment:
  Redmine version                          2.0.3.stable
  Ruby version                             1.8.7 (x86_64-linux)
  Rails version                            3.2.6
  Environment                              production
  Database adapter                         MySQL
  Redmine plugins:
  no plugin installed

Email configuration as follows:
  production:
   email_delivery:
     delivery_method: :async_smtp
     smtp_settings:
     address: smtp.yunzhisheng.cn
     port: 25
     domain: yunzhisheng.cn
     authentication: :login
     user_name: "redmine-admin@xxx.xx" 
       password: "xxxxxx"

development:
   email_delivery:
     delivery_method: :async_smtp
     smtp_settings:
       address: 127.0.0.1
      port: 25
      domain: xxx.xx
      authentication: :login
       user_name: redmine-admin@xxx.xx
       password: xxxxxx