Can the union mother post office send something?

You can't. The trade union mother station is a public service platform for employees and their families. It aims to provide convenient, high-quality and all-round services for employees, such as providing accommodation, medical care, legal consultation, cultural activities, legal education and other services for employees and their families, so it is not allowed to send anything. Express post is a place to send things, which is operated by express companies or third-party service providers, while trade union post is a place to provide services for trade union members and their families.