The Pella windows and doors direct mail kit features an interesting treatment to the outer envelope. The envelope is flood coated in black ink. Take a look at the images below of the face and back of the outer envelope.

Standing out in the mailbox is a large part of how you increase open rates. Typically the contents of a mailbox contain mostly white envelopes. When everything looks alike, it all tends to blend together. This is the opposite approach, and total opposite could make for a total win!