I believe that they have to scan the envelope for 
it to be able to be tracked though - a lot of the 
times I've gotten GP, they are in such a hurry 
and know that the cost is 5.00 that they just 
print out a label rather then enter the number by 
hand (most of the time they wont scan for the 
clerks).   I have started asking specifically to 
have that done though, just to be safe.

Volcheka