We have customized our own postmark that we apply before the letters ever go to a post office. We apply this special postmark on every letter we send out. That included with electronic postage. The huge Fairyland postmark is what really draws attention to it.
(This is a copy of the 2012 postmark that we attach to each letter.)
Our postmark changes each year and includes the year in big bold numbers!
So what is the return address on the letter and what does it look like?