I would like to know, what would be the best way to handle email alerts for missed calls. 

1) Only send the notification if the call was not answered at all. for example when it was ringing a group of extensions. Maybe use a special status code or custom event header?

2) When the call was answered by voicemail and only if the caller did not leave a voicemail, it should be considered missed.

3) If a caller hangs up a call within a IVR.

Thanks.

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