Voice mail situation in the conference using CTI Ports

Q. I have developed a conference application.It takes list of phone numbers as the input and creates conference using the CTI Port.

But if user passes the voice mail number in the phone number list, Voice mail is adding automatically in the conference.Some of the situations like Call forward to voice mail and call diverts to voice mail etc.

How to get rid of the voice mail situation?

A. It's normal case to add voice mail into the conference, if one of the call parties is voice mail number or divert to voice mail. For the conference port doesn't know what numbers are voice numbers.

To avoid this, maybe we have to drop off the call parties with voice mail numbers.