Apologies if this is already well known amongst our Australian Postcrossers.
I went to collect stamps for my newly acquired post crossing address and was informed by the Post Mistress that if the postcard sizes didn’t adhere to the dimensions listed in the photo then they would be charged at the large letter rate. A significant distance.
I hope this is helpful. 
I purchased some stamps this morning and they weren’t even sure how much it would cost to send to China. If the Post Office isn’t sure what hope do we have of getting it right 
I can’t even imagine. Everytime I walk into the PO it’s almost like it’s a “thing” 
Yes, it is a big difference, but the 1st set of dimensions is 5.1" X 9.4" & that’s quite a big postcard. Most are 4X6 and some are 5X7 but I’ve seen very few bigger than that.
They just keep chipping away at the services - a little price increase here, changing the requirements there.
Agreed. It’s just a helpful heads up for those that didn’t know and might have gotten caught by surprise at the PO. But yes quite large postcards. gratefully! 
My question is “what can you send that’s 250g but only 5mm thick?” To me, those dimensions don’t match up.
