The Vatican is a decision-making body in Catholicism that is capable of receiving letters and may occasionally buy important religious artifacts. (The X-Files: I Want to Believe; MM: "Owls")
In 1998, shortly after Millennium Group member Peter Watts informed Lara Means that the Group had spent a great deal of effort to acquire the Cross of the Crucifixion, Lara Means asked why that was, mentioning that she doubted the Millennium Group intended to sell the cross to the Vatican. (MM: "Owls")
Father Joseph Crissman – a former priest and convicted pedophile – later wrote dozens of letters to the Vatican, pleading re-engagement with the church. In 2008, FBI Special Agent in Charge Dakota Whitney learned of Father Joe's letters to the Vatican and mentioned them to FBI consultant Fox Mulder, upon expressing her skepticism regarding Father Joe's self-professed psychic ability. (The X-Files: I Want to Believe)