A mailto behavior is to define how Windows handles a mailto link, mostly on the web pages, when it’s clicked. The default behavior can change every time when a new program gets installed into your system. It’s usually handled through the default mail application installed on your computer but you can change it to use different method.
In Windows 8, it’s by default set to use the native Mail Windows 8 app but here is how you can change it.
1. Open Control Panel. You can do so easily press Win+X, and select Control Panel from power user menu that pops up.
2. Click Programs, and choose “Make a file type always open in a specific program”
3. In the next Window, find and highlight MailTo item from the long list of extensions. You should be able to locate it at near the bottom of the list.
4. Double click and pick one from the “metro style” popup.
5. Pick one from the list and Close. You are all set.
Note that this process is mainly for Windows 8. Though it’s pretty similar to Windows 7, I would suggest that you check out this post if you want to do the same on a Windows 7 computer.