Voicemail detection is not working

Question

I am using freeswitch v1.8 but what I found that voicemail detection feature is not working means when the calls goes out and if it is not answered by any human then FS should know that this call is answered by a machine not by some human

Answer 1

Voicemail is somewhat hard to detect because the telecom system/carrier doesn't tell us that a call has been answered by voicemail. It simply appears as if the call is answered by the other end. Our system attempts to detect voicemail (when that feature is turned on) by detecting the "beep" that typically precedes the chance for the caller to leave a recording. (e.g.: "The person you have reached is unavailable. You can leave a message. Beeeep.") This obviously doesn't work if:
The carrier voicemail prompt doesn't have a "beep" at the end or has some form of other prompt to ask if the caller wants to leave a message.