Ham marked as Spam with BAYES_99 - PhpMailer to old?

Hi there, I am running a small community page with PHP. Members can select notification e-mails on comments etc. Since today those e-mails - or basically all e-mails from the system - get taged as spam with a score of 3.5 that totally results to BAYES_99. How come? I am using PHP-Mailer 1.73. I am wondering if this will go away if I upgrade to 2.0. However I would rather not like to do that as a .0 release makes me a bit worried. Does anybody have an idea on how to eleminate that BAYES_99 score? Those mails are absolutly no spam. They contain a link to the commment page but that should not be the problem. At least it was not a problem for the last years. Any ideas? Thank you for any help, Merlin