Some advanced features would be, for example, if you're needing your API to send a call to a voicemail system, the voicemail system needs the 'forwarded from' h

Some advanced features would be, for example, if you're needing your API to send a call to a voicemail system, the voicemail system needs the 'forwarded from' header in addition to Caller ID so it knows what mailbox greeting to greet the caller with, whereas calling a voicemail pilot directly would just prompt the caller that a mailbox wasn't found and to try entering the 10 digit phone number. TelAPI solves this with ForwardedFrom optional parameter (see http://www.telapi.com/docs/api/rest/calls/make/ http://www.telapi.com/docs/api/rest/calls/make/)