Correspondence is just a way of political examination and investigation! Just look at some relevant information! See if you and your immediate family members (parents, children, brothers, close relatives) have a decent style, anti-party and anti-country remarks and behaviors, and have been sentenced! If it is a system such as the Public Security Bureau's Public Prosecution Law, it will be strictly controlled in this respect. General units mainly check the big principles and ignore the small problems! Most people can get by!
Generally, the time limit for completing the political review and inspection work is only 1-2 months. In some units, there are only a few people in the personnel department, and there are many things to do. It will take some time to copy this and post it in an envelope! As for how long it will take to deliver it, don't worry about it. Anyway, it's between the personnel departments of their respective units! They are responsible for implementation! Usually it's ordinary mail, and how to send this for some secret things is even more out of your control! Secret! Ha ha!
That's about it. After the interview, just wait for the employment announcement! Don't worry! Unless you and your family really have serious historical problems, if not, it doesn't matter! It takes two months from the end of the interview to the earliest employment! Wait patiently!