Cant set Mail as default email app

Mail is my email app. I also keep a copy of SeaMonkey in my apps to build home pages to run in Safari.

Occasionally I Save As an email from within Mail (shift-cmd-S). When I double click on that saved email, it always opens in SeaMonkey. If I right-click and select Open With - Mail.app (default), it will open in Mail.

I cannot get it to open in the default Mail.app by just double clicking on the eml file.

Is there any way to make Mail.app the default email app?