Anyone can send mail to an inmate at Leavenworth, the only list you need to be on is for the telephone and visitation. Be mindful that ALL mail is opened and checked by the staff for contraband before it's delivered to the inmate.
https://www.inmateaid.com/ask-the-inmate/at-leavenworth-detention-center-is-there-a-list-i-have-to-be-on-to-send-mail-or-are-they-allowed-to-get-mail-from-any-friends-and-family#answer
Accepted Answer Date Created: February 01,2013