Just to add my experience about normal Argentine post, sending parcels out with normal correo argentino is fine and has always worked for me. Receiving is a different matter. I always used my work address for things being sent to me (I work in an Embassy, people don't usually mess with mail to an embassy) I used to receive packages without a problem until my mum sent me a box with 3 maternity jerseys and some chocolates. That box completely disappeared. From that day on (10 years ago), anything sent in my name disappears completely. I even have to tell people sending me work documents that they can't put my name anywhere on the envelope otherwise it won't get to me.
I decided that my name must have ended up on a list of people who receive interesting goodies worth stealing, so they stop everything they see just in case there's something good in there.