Have a 3300 8.0 with a NuPoint blade on a MiCollab server for a Sheriff Department.
They use a Call Flow mailbox for call transfer points. When you call from an external number and choose a menu point and the call transfers (for example, dispatch) if they do not answer"after four rings you get, "thank you for calling the message center, please enter a mailbox number"
If you dial the Call Flow mailbox extension internally, and choose the transfer point, it doesn't happen.
The call flow is: speed dial number to call flow mailbox extension, blind transfer to ring group
Jim