The Latvijas Pasts, is the worst postal service I have ever experienced in any country I have lived or worked in.
Latvijas Pasts is so bad that about 75% of merchants on eBay Germany, France and UK will not ship to Latvia. If you ship a package or send a letter to Latvia from outside of Latvia there is only a 50% chance that it will be received by the intended recipient. If the package is received at all it takes at least a week longer to be received than in any western European country.
When I first moved to Latvia from the USA I shipped 3 packages filled with software discs, and important documents. I was told, at the US post office that they would take 2 weeks to arrive at my home in Latvia. The first box arrived in 1 month. The second package arrived in 3 months. It seems that the package was soaked completely during transit and Latvijas Pasts held it at their main receiving station because it weighed more than 4 kilos due to water content. When the package had dried and was back down to 4 kilos they delivered it to my post office for delivery. All the documents were completely destroyed. The third package never arrived.
Latvijas Pasts has a long way to go to become a modern postal service. I hope they accomplish that soon.
Riga Ratings 
I tend to agree that the Latvian POST is not a reliable service.
But in 12 years, I have NEVER lost a package sent in either direction and I send and receive over six packages or letters a month.
The Latvian POST does appear to have a huge DELAY in processing packages. They must have a very big building with a even larger pile of packages sitting around while the staff plays cards or something – besides working.