In the email, Jagex calls out the suspected behavior and offers the player a "one-time amnesty lifeline" to shape up. These players will be placed on a watch list and will be monitored for any further botting action. If the player persists in cheating, then Jagex promises to not only remove their account permanently but to include the player in a mass lawsuit.
"If you ignore our offer and instead continue use botting software, we reserve our rights to pursue statutory damages against you for between $200 to $2,500 per act of past, present, and/or future botting," the letter states.
A Jagex mod on the RuneScape forums confirmed that these emails are real.