can't be checked. Since anonymous letter is a kind of anonymous letter, it has no signature, no mailing address and no information related to the writer. Xinxin mailbox cannot be searched. Xinxin mailbox is a trademark name of Changde Xinxin Packaging Co., Ltd. The company was established on September 12, 28, and its registered place is located in Zhangshan Town, Changde Economic and Technological Development Zone.