Go to the Outbox CONSIGNOR, as you cross off the stack (Stack 1), which accumulates during the broadcasts of each carrier. If you have more carriers in the system, you will also notice that there are more piles. When you have checked for a bundle that activated Transmit Checked button, press this and accept the message that comes up.
Then it will pop up a window that runs through the transfer process. When the Outbox window is empty the information has been transmitted to the carrier.