Can an inmate refuse to receive my letters?

Yes. Inmates have the right to refuse incoming mail, and if they choose to do so the letter gets returned to the sender rather than delivered.

It is not something that happens often, but it does happen. An inmate may refuse mail from a specific person for any number of reasons, whether they want to cut off contact, are trying to avoid conflict inside, or simply do not want the correspondence. In some cases a facility can also flag or restrict mail from outside at the inmate's request, effectively blocking future letters from that sender.

If your letters are coming back refused, that is a direct signal from him. It is worth taking at face value rather than assuming it is a facility issue or a mistake. Mail that is refused is handled at the mailroom level and sent back, so it does not get lost or misrouted.

If you believe the refusal is not coming from him directly and something else is going on, you can contact the facility and ask whether there is a mail restriction in place and what the process is for addressing it. Beyond that, the decision to receive or refuse correspondence ultimately belongs to the inmate.