Post run at peak of diplomacy
Many believe that the regular and peaceful exchange of mailbags at Nathu La paved the way for the landmark agreement to restart border trade.
Every Wednesday and Sunday, a snow-chained Indian Army truck grinds its way to Nathu La from Gangtok. Simultaneously, a People's Liberation Army vehicle trundles up to the Tibetan side of the Himalayan crossing.
Then, in the freezing no-man's-land at the summit, and under the watchful eyes of troops from both sides, Indian and Chinese postmen exchange mailbags. For an estimated 100,000 Tibetans who live in Sikkim, and for those living elsewhere in northern India, it is the only means of getting letters to and from their relatives on the Chinese side of the border.
Mail has been exchanged in this way since 1995, when Beijing and New Delhi signed a treaty on confidence-building measures.
Before that, all mail for Tibet posted in India was taken to Calcutta, before being flown to Hong Kong and on via Beijing and Lhasa, taking months to reach smaller towns in Tibet. Apart from letters, which are censored at the Intelligence Bureau's Postal Research Centre in Silguri, 50km from Gangtok, the mailbags carry medicines and gifts.
Indian and Chinese officials say they are considering demands by the Tibetan community that mailbags be exchanged at least four times a week, instead of twice a week at present.