A bug has been discovered within the SpamAssassin rules sets that will
mark messages sent in the year 2010 (as of yesterday) and beyond with a
higher spam score than expected. This bug causes all mail to receive an
extra 3.4 SpamAssassin points and can result in legitimate mail being
flagged as spam.
This bug has been fixed by the SpamAssasin folks and you can update your
installation simply by running sa-update.
For a more detailed explanation and information on resolving this