Thanks Martin for finally reacting
.
I use a Zyxel Prestige 2602 (V3.40(MU.5)b3).
Tried putting on every option in my modem to get all the logging I can, but unfortunately it seems I can only see what happens inbound.
If I configure my VSP Budgetphone directly in my modem, busy detection is happening, because I can hear a busy tone when the phone is off the hook and call my own number with my cell phone.
When I do it via Voxalot again, and the VM is off, I get no busy tone, but it seems the line is connected and disconnected at once (so, not even a 'dead line' anymore).
When VM is on, the unavailable message is playing at once (not waiting for the time I had configured, so the system must know someway I am busy, because when I am not it will wait for 25 secs before the VM kicks in.
Thanks again for looking in to this. If there is anything I can do to help testing please let me know.