It has to go through the mailroom process at the facility. He should have it in his hands within 6-7 days of sending, max
https://www.inmateaid.com/ask-the-inmate/i-sent-a-postcard-to-my-friend-through-inmate-aid-how-long-until-he-gets-it-39-s-can-he-respond-right-away#answer
Accepted Answer Date Created: January 27,2022