HBO’s Power of the Letter campaign encourages consumers to customize one of six different greeting cards carrying quotes from John Adams and his wife, Abigail, and send the cards for free.

The cards, available through March 30, are intended to build awareness for the HBO mini-series by encouraging people to emulate the letter writing of Adams and his wife who exchanged more than 1,000 letters in their lifetimes.

HBO’s seven-part “John Adams” debuts on March 16.