Receiving a Busy Signal/Call Drop when a Call Queue Forwards out to an External Line 

Updated: 04/07/2026

Symptom

When using a Call Queue to dial out to an external line, you receive a busy signal/call drop.

Applies to

  • Admin Console 
  • Call Queues

Resolution

For a Call Queue to forward calls out to an external number, the phone number receiving the inbound call must be assigned to a user or service first. An unassigned number will not support forwarding to an off‑net (external) destination.  You need to involve a user/number in some way:
 
  • One method would be to assign a number to the Call Queue. 
  • Another method is to forward calls from the Call Queue to a user or Auto Attendant and then configure that user/Auto Attendant’s call forwarding rules to dial out to the external number.
 
The above approaches rely on a number being associated with either the Call Queue, with a user or extension that handles the external forwarding. 
 
Note: Essentially, when placing a call to the Call Queue to eventually dial out to the external line from the Call Queue that is not assigned to a number, there is no phone number to associate with the call, and the carrier rejects it with a 403 FORBIDDEN.

Causes

  • Concurrent external calls has been reached
  • No user/service/number is assigned to the Call Queue