I've just gotten notification that many of your accounts on my server were disabled due to excessive bounces, and all of those bounce notices were from gmail addresses. I dug a little deeper, and it seems Google changed the auth requirements for sending email to any gmail.com http://gmail.com/ account.
I don't have time right now to spend on this, but I will try to update things soon. And yes, I know that the people who are affected won't be able to receive this post, but maybe they'll be curious and check the archives.
-- Ed Leafe