Making A Conference Call From An Email - HTC hd2 User Manual

 Chapter 2 Phone Calls
To end the conference call and stay connected with the private
call, tap Menu > End Active Calls. To end the private call and the
conference call, tap Menu > End All Calls. If you do not have any
private call, tapping the End Call button at the bottom of the screen
ends the conference call.

Making a conference call from an email

From a received email message, you can directly start a conference
call with the sender and other recipients of the email if you have their
phone numbers stored in your contacts.
For more information about starting a conference call from a received
email, see Chapter 8.