Was able to repro this on 5.4b14 and 5.3.4f1 on Win 8.1 using the 2.4SDK, however I think this is a Tizen bug as the app that crashes is the Tizen email program:

1) Application.OpenURL works for opening URLs (I tried http://www.google.com)

2) It does NOT work for mailto: protocol. I tried doing this with the "Email" capabilities box checked and not.

To repro:
1) Paste the following code into an OnGUI function:

if (GUI.Button (new Rect (100, 100, 100, 100), "Press to open browser"))
Application.OpenURL("http://www.google.com");
if (GUI.Button (new Rect (300, 300, 100, 100), "Press to send email"))
Application.OpenURL("mailto:blerk@unity3d.com");
2) Put that script on the camera in a blank scene
3) Push to device
4) Press button 1: It opens browser
5) Press button 2: It opens the email program; email program then crashes
6) Repeat steps 4-5, but check the capability "email" box in Build Settings > Publishing Settings first.