Official letters can be sent to government units at the same level, or to higher authorities or lower authorities. The contents of the official letter can be to exchange information, ask for help, report work to superiors, ask for instructions, give instructions to subordinates, and issue notices. "Shang Qi" is common in the language at the end of official letters, which generally means "send Shang Qi", which is a polite blessing to individuals and companies. Shun: By the way, I wish business: Doing business: Auspicious and Shun Song: By the way, I wish my work or the business development of the company all the best.