package send through the post office has a cheaper rate compared to couriers like DHL.
takes a long time (10-60 days) to reach the destination country.
handling also sucks, so avoid fragile items.
other than that, both are the same. they get the job done.
rate is mostly flat and don't change much if:
- package physical weight per 1kg. weigh more = rate goes up.
- package size. for a large package which don't meet their standard size, they will ignore the actual physical weight, and calculate the rate based on volumetric weight. custom packaging usually ends up with volumetric weight rate, so beware.
- destination country.
different country, different custom regulations. the post office/courier will tell you more.
that's pretty much about it.
USPS International Priority Mail is good enough for sending non-urgent items in a bubble wrapped envelope (14-20 days to reach most South East Asia countries)