I'm having trouble registering a SipStation account. They require username:password@trunk1.freepbx.com to be sent to the registrar. I've done a bit of searching but was unable to find any specific details on how to do this. My config is as follows:

<include>
    <gateway name="SipStation">
      <param name="username" value="myUsername"/>
      <param name="password" value="somePassword"/>
      <param name="realm" value="trunk1.freepbx.com"/>
      <param name="from-user" value="TriTelComm"/>
      <param name="proxy" value="trunk1.freepbx.com"/>
      <param name="expire-seconds" value="800"/>
      <param name="register" value="true"/>
      <param name="retry-seconds" value="60"/>
      <param name="context" value="public"/>
    </gateway>
</include>