The market for postal services in Germany has been deregulated, meaning that private companies are allowed to deliver both letters and packages. For private individuals sending a normal letter, the German postal service however remains the best option. The rates are not cheap (62 cents for a 20 gram letter), but the system is quick and efficient.
Mail in Germany is delivered early in the day, usually before 10 a.m. Sometimes letter carriers will leave packages with neighbors, but there's no guarantee. If you get a package and aren't home to receive it, you'll receive a form that tells you where and when to collect it. When you go to pick it up, don't forget to bring identification with you (passport or EU driver's license).
To send packages weighing more than two kilos, you should definitely consider using one of the private competitors which often have better rates than the Deutsche Post. The major private postal companies are TNT Post (www.tntpost.de), Hermes (www.hermes-logistik-gruppe.de) and GLS (www.gls-germany.com). In particular, Hermes has a good network of dropoff points for packages, such as supermarkets, news agents, dry cleaners, etc...which are often more convenient than the post office. If you want to compare postal prices from several different suppliers, a helpful website is www.posttip.de
For express mail services within Germany, the postal system is as good as any other private company. Actually, Deutsche Post purchased DHL several years ago and it is competing in the private market place. Many letters arrive usually overnight in Germany without an extra charge (part of standard delivery). If you’ve got to be sure, send it express and your mail will definitely arrive the next day. FedEx, TNT and UPS also operate in Germany and can help with express mail outside Germany. Most post offices are well-equipped with supplies so that you can buy a box to hold what you want to mail, wrap it and send it off all directly from the post office.