Postal services from Sri Lanka (slpost.gov.lk) are fairly reliable, at least as far as airmail is concerned, which, for example, takes three to four days to be delivered to the UK, Russia or the USA. The cost of land or sea delivery is from one third to half the cost of airmail, but is terribly slow and involves great risks of loss or damage in transit. A postcard to the UK, Australia or North America costs 25 rupees ($0.16). Sending parcels by air mail to the UK will cost about $17 for 0.5 kg; in North America as well, and in Australia a little cheaper. If you want to send a parcel home from Sri Lanka, do not immediately pack the contents, it must be checked at the post office before packing (all major post offices have scales, glue, wrapping paper and twine).
Another option – “EMS Speed Post”, which is a little faster, but also more expensive than the state airmail – sending 0.5 kg to Europe costs about $20 (a little more in North America and Australia). In addition, in Colombo you can find a number of well-known international delivery services.