Welcome to Mitel Forums. The Mitel resource - by techies, for techies...
Do they require a Deskphone or happy with a softphone?I have also configured a SIP softphone (many free ones out there) on a PC that has a VPN to the office network. That will get past the firewall issue but it does affect the audio if the bandwidth is not good.This is more a networking question than a phone one to be honest.