For debugging it would be very helpful if an Admin could test the media types bound to a user. This should go to Administration --> Users --> userid --> Media, next to Enabled, Edit and Remove. Verification could become part of the "add user procedure".

The test feature in Administration --> Media Types is not sufficient, because it cannot send a message to a user. It verifies the message script, but not the User's sendto parameter (EMail address, cell phone number, etc.)