It appears that I am letting the PBX send internal call information through the SIP to the provider. If I call an internal extension, including the 9999 voice mail number, I get a 3CX email back with an error. I don't want to deselect the "Trunk/Provider responds to Request with an Error code" email selection but reduce the amount of errors I send to them. I thought it might be that I didn't define "Calls to Numbers with a length of", but when I entered "7,10,11", the error went from: . 484 Address Incomplete to: . 403 From: URI not recognized I saw this in a few other threads that were already closed for comments, and the ones that had a response were suggesting to deselect the "Trunk/Provider responds to Request with an Error code" email button. I'd like to not send internal extensions and the voicemail code to the SIP. I'll keep trying things, and will respond if I do figure it out, myself. Any suggestions are greatly appreciated!