Can IP-Phones via STUN be used?

No, 3CX does not support IP-Phone in STUN while hosted by 3CX. 
Here are our recommendations to connect to 3CX:

  • For the Home Office:
    We strongly recommend using the 3CX APPs and/or Browser-Extensions which are simple, feature-rich, easy to use and are included free of charge in your subscription.

  • I have a remote Office:
    We still recommend the 3CX APPs and/or Browser-Extensions, however, to connect multiple IP-Phones from a single office space, use the 3CX SBC. The SBC overcomes network and firewall configuration/hurdles and also reduces the bandwidth requirement for calls. One SBC is required per office space.