Inmates may reject mail without opening it. We are not 100% sure that is the reason in this case, but if there are hard feelings or it's a recent incarceration, the inmate might be a little out of sorts.
https://www.inmateaid.com/ask-the-inmate/why-would-i-get-a-letter-returned-quot-refused-quot-if-my-family-member-a-cousin-is-at-that-facility-does-that-mean-he-refused-my-letter#answer
Accepted Answer Date Created: August 25,2017