I have a SIP door phone set up on a MiVo250. Users can call from any Mitel IP phone extension to the door phone (SIP ext) and when it answers they dial the 'relay' code (built-in to door phone) and it triggers just fine. However, if the door phone initiates a call to another Mitel IP extension and it answers, the door phone does not recognize any touch tones entered by the user on the IP phone. So, I essentially have one-way DTMF working. Any thoughts on what is causing this?? Thx!