AFPEx and Flight planning top tip - to receive a copy of the FP youself, add your AFPEx address in one of the address boxes at the top
I am advised by the staff at Swanwick that you absolutely should not do this, because it triggers an alarm at their end; this is to prevent messages looping back indefinitely in some circumstances.
The only way to check that a VFR flight plan has been transmitted is to look in your Outbox, and it should be there. That's the way VFR flight plans are... there is no way to know (short of a phone call etc) anybody has seen it or even got it.