Australian Army - Middle East - WW2

[Michael Dobbs]

I have received the following enquiry

[color=maroon]My father served in the Australian Army in ww2 in the middle east. He sent letters home in blue envelopes with BY AIR MAIL printed on them. They did not have stamps. Was the airmail service free or was the postage included in the purchase of the envelopes? I would be grateful for any help you could give me. [/color]

I have responded to ask for a scan of the cover, but can anyone help with the question please ?

Thanks, Mike