yes, the cards are prison-approved and are in the pre-stamped format
https://www.inmateaid.com/ask-the-inmate/does-inmateaid-post-card-have-a-pre-stamp-on-them-where-my-boyfriend-is-located-thw-mail-and-post-cards-have-to-have-postcard-prestamped#answer
Accepted Answer Date Created: September 15,2019