If you are a fan of minimalism website icon pack, then (Freebie Friday) – Envelope icon is best choice. Todays special is a collection of Free (Freebie Friday) – Envelope icon that you can customise as you see fit.
Download royalty free icon file and use it as you wish to use it. The PSD Mockup created by Dribbble.com.
If you want more icon, you can check the Free Icons.