If I sent a letter and it could not be delivered (lack of postage) then would the Royal Mail centre open it up, find out who sent it, and send it back? They did when I incorrectly addressed one twelve years ago. Sent a letter about two weeks ago - five pages of A4. I put it in a DL (ie third of A4 height) envelope, but did not flatten it. However, it was less than 5 mm think so that should be ok. Or so I thought... However, last week I sent a letter with five sheets of A4 via recorded delivery, but the woman at the post office insisted on flattening the letter. Should be ok, shouldn't it? It really does need to get there. BTW, no drugs or porn or anything dodgy were involved, the contents will not result in being put in prison or a padded cell. It would be nice/useful if they did get to the intended recipient though.. Posted here as I can't be ARRSED finding a more suitable forum.