[KingDead]

Nope, not in the US. And just sent an envelope. Another user reported this working for Adidas in the US.

That user was me. Might be because you are not in the US.
Did you use a bubble envelope roughly 6x9inches or smaller or just like a letter envelope?

I've done it with about a dozen retailers and while not every retailer worked I never received an email telling me they received an empty envelope.

You can try an FTID envelope return.
Or go to the carriers website and get the proof of delivery of the envelope and initiate a chargeback showing they received it.

Don't give up and message me for more help.

Also was the envelope completely empty or did you put the  paper that details the return they sometimes tell you to put in the envelope?  I never put that paper in the envelope.

So this wouldn't work outside of the US ? (Envelop method from France to Germany for example)

I'm glad to be back after another mernal health issue. 15 days rotting in a hospital thinking about new scams.

Im not sure. I don't know whaqt carriers you have if you have drop boxes. I have no idea what policy DHL uses if that in your area.

ask @mothered Not sure where he lives but he runs this website, all of it not just this SE section so he probably klnows people in Europe.

Or you could do a deep dive on each delivery companies policies for each country. A dry read for shore but all you need is one little paragrash that solves the problem.

Sorry I couln't be more helpful. I admit to a small degree to being one of those Americans that forgets alot of members on here, hell maybe half are not in the USA SE'ing retailers.