Hello deviantArt, this is my first submitted icon, please enjoy! This is a replacement icon for any mail app, and the icon sizes are mainly for Mac OS X. However, the 16x16, the 32x32 and the 256x256 will work in Windows—and, if you change Windows' icon sizes, you'll be able to use all of 'em (although I really don't recommend that, you might run into big problems), and same thing for Linux, I guess, and the 16x16 will work with the default sizes. You could also use the 256x256 icon for the iPhone if you want to.
It comes in .icns format and in an iContainer, ask me if you want a .ico format, or the .png's
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