I'm aware of that. Heh, you weren't seriously trying to teach me Copyright Law, were you?
An individual sending someone a DVD through the post without charge is not copyright infringement. The lending right covers only establishments available to the public at large (so private lending is not included). The RENTAL right covers private individuals but to be "renting" it you need to be making direct or indirect financial benefit. The "making available" right only covers electronic means or broadcast. So long as no copying is taking place in this exchange, it's not copyright infringement.
It's no different to re-selling of a copyright work. If you buy a DVD and no longer want it, you're entitled to re-sell it, because the physical content-holder (the DVD itself) belongs to you, only the material on it is protected. It's the like the old argument over who owns a letter, the author (who owns the copyright) or the recipient (who, once they receive it, owns the paper it's on). That was disputed with Diana's letters to Hewitt, where it was decided that he was allowed to sell them, but any paper he sold them to would not be allowed to publish them (as this would breach the copyright). The law seeks to balance these two rights in a way that protects authors without hampering private individuals' freedom of contract.