A bug fixed for Y2K in spamassassin unfortunately left another bug for
2010. This caused a rule FH_DATE_PAST_20XX to flag for every email sent
Depending on how your rules are structured, this could lead to mails
being marked as spam.
Spamassassin has a patch available which will fix this error. If you
cannot run sa-update to install the patch, you can disable this check by
score FH_DATE_PAST_20XX 0
In your spamassassin local.cf file.