Clicking Paper

Hey all! I have this script to allow the player to click a piece of paper and a gui texture appears on the screen to allow them to read the paper. When I click the paper, however, it isn't working. Any help? var email : GUITexture; function Start() { email.enabled = false; } function OnMouseDown(){ if(gameObject.tag == "paper") email.enabled = true; } function Update() { if(Input.GetKeyDown(KeyCode.E)) { email.enabled = false; } }