Colombia doesn't have a postal service, it has a group of blaggards and thieves that you can buy stamps from and then they steal or lose your mail. It is called 4-72www.4-72.com.co
4-72 is the approximate coordinates of the middle of Colombia Latitude 4 Longitude 72. That's where the name comes from
4-72 is a private company which I believe rose from the ashes of Adpostal which was the previous state run postal system. It is a bit before my time but I hear that Adpostal was even worse than 4-72 which is difficult to believe.
4-72 is the defacto recipient of mail sent to Colombia from other national postal systems. For example, you address a letter to Colombia and send it via Royal Mail in the UK or USPS in the USA and then 4-72 receives it and subsequently loses it or steals it if it looks like it might have something interesting inside. This obviously means that Royal Mail and USPS don't have to come all the way to Colombia to lose your mail themselves.
Most companies don't use 4-72, for example Telmex uses Servilla S.A. to deliver its invoices, Telefonica uses a messenger service, Codensa and Acueducto delivers its own mail, UNE Empresas Publicas de Medellín uses LanPostal, Helm Bank uses Puntual Correos,
Colombians also don't seem to use envelopes, they tie your correspondence in a knot and put a staple through it so it rips apart when you try to open it.