I have 3 remote extensions with Snom phones and are working but some times i say very often when a call from one ext to another they apper to be register but they do not ring the send me to VM , what can i do so they will work better, they are all behind routers or nats
if i activate stun which setting should i use ,? which is the server of stun,
Stun.epygi.com ? or stun1.epygi.com and what port ? for the phones .

Thanks for your help .