In Switchvox v. 6.2 and above, a Caller ID Number must be 7 digits or longer to be considered valid. If a shorter number is used (less than 7 digits), the PBX would treat it as an internal Caller ID Number, and the PBX would set the outgoing Caller ID Number to 'Unknown' (with no Caller ID name).
When setting the Caller ID Number under VoIP Provider > Caller ID Settings > Caller ID Number, the field should have a number is at least 7 digits in length.
When user creates an Outgoing Caller ID Rule (Setup > Outgoing Calls > Caller ID Rules tab), the field: caller id number to should contain a number that is at least 7 digits. The Switchvox will then pass the Caller ID based upon the call rules.