I don't know if the site uses "mail city" as an equivalent to capital, because it also says "Hanoi is the mail city of Vietnam" (it's the capital but the largest city is Saigon/Ho Chi Minh, so it's debatable which one is the "main" one).
It's also full of other typos and badly formatted text, which I think is due to the data coming from a quick scrape of a source of dubious quality.