Legal analysis: Circular letter is a kind of weekly sexual knowledge official document suitable for publishing matters that should be observed or known within a certain range. Notice has the characteristics of literal information, clarity and certain restriction. Because most of the contents of the notice involve specific business activities or work, the notice also has professional characteristics in content.

Legal basis: Article 84 of People's Republic of China (PRC) Civil Procedure Law * * * The service of litigation documents must have a receipt, and the addressee shall record the date of receipt on the receipt and sign or seal it.