Envelopes are essential elements of any company's stationery needs, just like letterheads and business cards. For any larger company, envelope design is also a form of marketing or brand image promotion.
Generally, the envelope should include the company logo as well as the address and sometimes other things such as advertising a particular product or service of the company. Why not take advantage of the free space?
This free envelope mockup comes in Photoshop format with smart object support. Although it is minimalistic, feel free to use the remaining space in any way you want besides inserting your logo and contact details.
Next, we have nothing else to do but to thank the author of Deep Yellow for sharing this nice mock-up of the envelope.