You were lucky to get it back. As I understand from the USPS site (I remember reading it on there, but have no idea where to find it again) there are no reciprocal arrangements for collecting unpaid postage internationally and it would normally be RTS.

In the UK it works the same, it will either be RTS or sent to the dead letter office and destroyed.

Which is a very good reason to always be careful to put enough stamps on!

So I've searched for a thread about my situation but I didn't find it so,

I live in Europe and I am not able to get IRCs so I usually send out LORs and SAEs. Today I recieved a great succes from the United States. The SAE was delivered to me fine but there was no postage added to the envelope.

Instead it had a red stamp with [b]"Postage Due___" [/b]stamped upon it. But no amount was written and I did not recieve a note from the postage company inside or anything. There isn't a date mark either anywhere either?

Did this happen to anyone?