Any mail that comes into the prison is inspected by the staff for contraband. Typically the daily received mail makes it to mail call the same day (Monday-Friday).
https://www.inmateaid.com/ask-the-inmate/okay-when-the-books-are-shipped-from-amazoncom-the-books-are-delived-to-the-prison-they-got-there-friday-when-do-the-prison-give-the-books-to-the-inmate-when-do-the-inmate-get-the-books-and-thank-you-for-answering-my-question#answer
Accepted Answer Date Created: March 10,2013