Quote:
... I have read elsewhere that using the actual home language of the country would help immensely.
Is most true, Puzzler, is more to most true <== machine translation joke
I apply a self-adhesive address-size (1*3ish) Avery label, in the language of the receiving country, to every packet: "Contains photographs."
This explains the stiffener, the lack of a Customs declaration, and the worthlessness of the contents.
I have done this with stamps in approval cards, postcards, and DVDs.
For the latter, I use two thinner stiffeners - cut from breakfast cereal boxes, if you must know - to hid the shape.
For the label text, I use two different translators: one to go into the target language, and one to take that translation back into English. When it works *both* ways, I figure it'll work.
When I was a letter carrier, ages ago, USPS was viciously disciplined about getting signatures, step-by-step, for Registered Mail ... of US origin.
Foreign stuff might show-up in the regular mail stream, uncounted & unregistered and, if you pointed this out, you were told that it was your lucky day, because you could just toss that one in the recipient's mailbox, sans receipt.
CYA, the truly Universal Postal Union.
I am not sure why any American would expect even Registered Mail of American origin to get vastly more respectful treatment wherever it travels.
Cheers,
/s/ ikeyPikey