Is this wrong??

I know its not really wrong but I feel weird about it....

I got my first Holiday card of the season, from my wonderful friends at AGS, Lori and Mike. They have a courier service, which I think dropped off the cards, so they didn't go through the mail. They DID however, put a stamp on it. A pretty X-mas one like below. Is it ok for me to use that stamp because technically it hasn't been used right??