We are also seeing more obvious spam in our inbox and normal mail in the spam box.
When I say obvious spam these are drug and sex e-mails that should have been picked out just by the subject lines.
Is it possible someone is sabatoging the automatic filtering system by clicking these e-mails as "NOT SPAM" thereby fooling the system? Just a thought. If enough people (spammers with multiple accounts) did it it might work.