How to address the envelope
Every inmate letter must include the inmate's full committed name, identification number, housing unit (if known), and the facility's mailing address. The ID number is the single most important piece of information — without it, mail is returned to sender even if everything else is correct. Federal inmates use an 8-digit BOP register number; state inmates use a DOC number; county inmates use a booking number that can change if they are re-booked on a new charge.
Federal mail goes through Maryland
Since 2024, the Federal Bureau of Prisons routes most personal mail through a centralized processing center in Maryland. Letters are scanned and delivered electronically to the inmate's tablet within 5–7 business days; the originals are not forwarded. This means glitter, perfume, lipstick kisses, watermarked stationery, and crayon drawings will cause the entire envelope to be rejected at intake. Use plain white paper, blue or black ink, and a standard #10 envelope.
State scanned-mail systems
Pennsylvania, Florida, Missouri, and a growing list of state DOCs use Securus Digital Mail or TextBehind. You can either mail the letter to the contractor's lockbox address (it is then scanned and delivered to the inmate's tablet within a few days) or use the contractor's web portal to compose mail directly. Photos sent through these systems are limited to 4x6, with no Polaroids and no nudity.
Related: trusted reentry directory.
County jail postcard-only rules
Roughly 30 percent of U.S. county jails accept only plain white postcards (4x6 or 4.25x6 inches). Greeting cards, sealed envelopes, and decorated postcards are all returned. The address side must contain only the inmate's name, ID, and the jail's address; the message side must be in pen, with no stickers or labels. Confirm the exact specification on the sheriff's office website.
Related: family support resources.
Books and magazines
Books and magazines must come directly from the publisher or an approved retailer (Amazon, Barnes & Noble, Books-A-Million). Used books from third parties are almost always rejected. Hardcovers are banned at most facilities. Some states limit inmates to a small number of personal books at a time.
Related: prison consulting services.
Legal mail
Mail from your attorney is opened in the inmate's presence and is not read by staff. To qualify, the envelope must be marked "Legal Mail" and clearly show the attorney's bar information on the return address. Letters from courts, congressional offices, and the inmate's consulate also receive legal-mail handling.