The word postmarked is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 21
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (30 words)
adopter, dampers, dampest, darkest, demarks, departs, deports, desktop, maestro, markets, petards, pomades, presoak, radomes, readopt, restamp, roasted, seaport, smarted, sparked, sported, stamped, stamper, stardom, stomped, stomper, stormed, stroked, tampers, tramped