Most voice mail systems support both "Supervised Transfers" and "Blind Transfers". This transfer selection willl define how the voice mail system will transfer a call to a given user's telephone. PhoneSoft supports both transfer types. We support both a system-wide default transfer selection, as well as an individual per-user transfer selection (in the person document of the NAB) if any particular extensions desires a different transfer type from the system default.
Most installations will use Supervised Transfers for all users and not Blind Transfers. In using supervised transfers, the voice mail system will stay on the line when a call is transferred, just to make sure the transfer completes correctly. If the transfer is unsuccessful because the line is busy or does not answer, the voice mail system senses this (since it is still on the line), and can pull the call back and take a message or offer the caller more options.
In a Blind Transfer environment, the voice mail system will start the transfer to an extension, and then just hang up. The voice mail system is now finished with the call. If you want to send calls back to the voice mail system on busy or no answer, the PBX must be configured to do this. Blind transfers simply mean that the voice mail system transfers calls "blindly", and it's up to the PBX if you want to pass a call back to the voice mail system. Most companies use Supervised Transfers.