Oh, by-the-way, when I worked at the prison, I logged in the mail but didn't read it. I worked nights (7p-7a) & just did what the day shift didn't get done. Most of the letters, etc had already been processed & passed out. Most I had to log in was the 3rd class - newspapers & mags, etc.
YES, they told me some wild stories about mail that was incoming/outgoing. So, it is "SCANNED" to an extent, but rarely read.
At county, the jail administration did the mail. The COs didn't have anything to do but pass it out when it came our way. I think they scrutinized the mail more at county, mainly because there wasn't as many (only about 100+ inmates) compared to 1500+ inmates at the prison. The prisons are dealing with sheer volumes of letters/mail.
Read what Law Dog wrote about it on another thread. This has been addressed before.
Thank you & God bless <><n