In an effort to celebrate mail, the US Postal Service has joined with HBO to spotlight founding father and prolific letter-writer John Adams. The "Power of the Letter" campaign, running until the end of this month, promotes HBO's epic miniseries John Adams, which premieres on March 16. It also drives viewers to visit www.poweroftheletter.com to create and customize greeting cards with quotes from John Adams and his wife Abigail that were created by the USPS' online retail partner Cardstore. Visitors can also enter a sweepstakes to win a VIP trip for four to Colonial Williamsburg.