Redirect to correct domain in IIS

gistfile1.xml

<!--
  - Redirect to correct domain in IIS
  - Useful if you have more than one domain
  - for example: maindomain.com, maindomain.co.uk, www.maindomain.co.uk, testingdomain.dev
  - inspired by https://github.com/paulirish/html5-boilerplate-server-configs/blob/master/web.config#L192
  -->

        <rewrite>
          <rules>
            <rule name="Correct Domain" stopProcessing="true">
              <match url="^(.*)$" />
              <conditions>
                <add input="{HTTP_HOST}" pattern="^(?!www\.maindomain\.com)(.*)$" />
              </conditions>
              <action type="Redirect" url="http://www.maindomain.com{PATH_INFO}" redirectType="Permanent" />
            </rule>
          </rules>
        </rewrite>