Can i get arrested for sending a semi threatening letter?

i just sent a threatening letter, well not life threatening specifically to someone using an anonymous email, i know it sounds creepy but if you knew this person you would probably be on my side. and apparently she said shes got my ip address and is going to give it to the police,. admittedly this was the wrong way to go about things and i regret doing it in a way, can i be arrested for this?