There is no definitive source for restrictions on prisoners' mail. While all federal prisons are run by the Federal Bureau of Prisons, each institution has a level of autonomy over their mail restrictions. State, county, and local prisons and jails vary widely in their mail restrictions which are often determined by individual department of corrections commissioners or wardens depending on the state. The prisoner is the best source for finding out what can be received. Prisoner support activists recommend asking the prisoner directly via a letter before mailing any packages. Ask them exactly what they can receive and how frequently.
Books to Prisoners groups are a good reference source for learning more about sending materials to prisoners since at prisoners' requests they send thousands of book packages every year. They track mail restrictions in order to do their work. The two largest groups are Prison Book Program in Boston and Books Through Bars in Philadelphia.
Links:
- Federal Bureau of Prisons
- PrisonsandJails.com: Guiding Corrections Through the 21st Century [provides contact information for state, county, and some local prisons & jails]
- Prison Book Program
- Books Through Bars
