REST API Ringout results - is it possible to tell if the recipient never answered or if the call went to voicemail?

You'll need to query the call log data from the other side of the call (the recipient side, which would be one of your RingCentral users).

You can do this in one of two ways:

1. Call Logs by Extension (as Recipient)
-or-
2. Call Logs as Admin User (and filter by Extension.id + session.id)

The reason for this is because every call has at least two parties: caller (person placing the call) and callee (recipient of the call being placed).

If you are fetching the call logs from the callers side (as your initial data indicated with the 'direction' property set to "Outbound"), then yes, you will only ever see "CallConnected" if the call was actually connected.

You'll need to GET the call-log data for the "callee". Then you should see the different statuses which will indicate either 'Missed' or 'VoiceMail'.

ok, I understand, but that would only work if the callee is a ring central user. In our case we are using the Ringout feature and the callee could be anyone. 

To try and determine this for outbound calls, you'll have to mix and match your programming logic between call log and message store data.

You might ask how to do this in Stackoverflow (use the 'ringcentral' tag), since there are a lot more developers there who love to answer questions (and we're moving towards that system for technical questions anyway). You should reference this conversation in the question on SO.