If you happen to need to ship anything from Vietnam, you may be interested in the response I just gave someone:
By normal post it's always been extremely slow to ship anything (anywhere from several weeks to several months), and things have a tendency to break. If you are sending anything that might break, I recommend using one of the Styrofoam boxes used for packing seafood. You can often find them for sale--very cheap--at shops near docks, ports and harbor areas.
Couriers are much faster--I've averaged almost two weeks no matter who I use. They are of course very expensive. DHL and EMS have been cheapest and provide good service. Many of the couriers have free pick-up service, the only problem is you have to wait around half the day, or all day, and they may not show up at all. For that reason I find it best to schedule the pickup for toward the end of the day, so your waiting is at a minimum. The post office often has a pickup service but I've encountered some corruption and unreliability with it.
Note that whatever you mail, particularly large boxes of mixed items, will be unpacked and searched before it is shipped. This can cause problems if you brought it already safely packed because all of that will be re-done and might be re-packed haphazardly. Make sure you insert yourself into the situation so you can control how it is re-packed.
Note that media like DVDs and CD's with movies and music can not be mailed back, at least unless it has the little government-certified stickers on it. Photo CDs and whatnot are fine. I've never mailed books out of the country, but that might be a problem.