I sent a gift to a friend in Spain: t-shirt inside a big envelope. Took it to a swiss post-office (www.poste.ch) and paid 3 euros. Seven days later a letter from the post-office says I paid too less. It should have been 5 euros (because was more than 2cm thick). Not clear if they had sent the envelope or not. In post-office they did not accept their error and could not tell where the envelope might be.
I did not pay the 2 euros difference. Twelve days later my friend did not receive yet his gift. Swiss post sucks. What a pleasure to say.
(this comes in consequence of my birthday gift, sent in Swiss express mail due to arrive before 9am my birthday, arrived on mid-afternoon and I could only pick it up the next day).