I too received my letter today.
Everyone who feels the need to write should send their letters to:
[email protected]
[email protected] (Prod Mgr-united.com)
[email protected] (CEO and Chairman)
[email protected] (IS and CIO)
[email protected] (VP E-Commerce)
Don't delay - it will take a serious effort to get UA to put off a July 20th cutoff of the software.