This has been bouncing around other news outlets, but I’ll mention it here: There’s an out of data SpamAssassin rule that can potentially mark mail as spam because of the 2010 date.  A mail to tech-pkg@netbsd.org describes the various fixes.

The step of ‘sa-update && /etc/rc.d/spamd restart’ seems to have fixed it for me.  Incidentally, if you are using SpamAssassin, sa-update is a good tool to run on a regular basis.