The Snom phone is able to dial out but when the call is picked up there is no sound on the Snom end and loud static noise on the external end. For the SIP DECT phones, they're not able to dial out at all, it just says unavailable right away. For these, I've tried starting the dialed number with 9 as I am doing on the Snom device and dialing just the external number.
The NAT type was set to native so I changed it to NAT. After doing this the static noise on the Snom call disappeared but now there is no sound at all on either end. I have not tried the other SIP handsets yet as I'll need to be in the office tomorrow to test them.