Provider XO Communications (USA)

used as an outbound gate with this configuration

<include>
     <gateway name="XO">
          <param name="proxy" value="205.X.X.X"/>
          <param name="register" value="false"/>
          <param name="caller-id-in-from" value="true"/> 
          <param name="username" value="not-used"/>
          <param name="password" value="not-used"/>
          <param name="t38-passthru" value="true"/>
     </gateway>
</include>