The Japanese postal system is extremely reliable, efficient and, for regular postcards and airmail letters, not markedly more expensive than in other developed countries.
The airmail rate for postcards is ¥70 to any overseas destination; aerograms cost ¥90. Letters weighing less than 25g are ¥90 to other countries within Asia, ¥110 to North America, Europe or Oceania (including Australia and New Zealand), and ¥130 to Africa and South America.
If you want to ship purchases back, boxes are available for purchase at post offices.
One peculiarity of the Japanese postal system is that you will be charged extra if your writing runs over onto the address side (the right side) of a postcard.
The symbol for post offices is a red T with a bar across the top on a white background (〒).
Mail can be sent to, from or within Japan when addressed in English (Roman script).