An indie rock duo took the name the Postal Service in honor of the way it wrote its songs, by snail mail. One musician lives in Seattle, the other in Los Angeles. The U.S. Postal Service learned about the band and sent a letter to the band, demanding it cease and desist. But last week, they struck a deal. The band keeps its name, but advertises for the U.S. Postal Service, which hopes to get young fans sending more letters.