If you are receiving a flood of email with the statement of  *****POSSIBLE SPAM***** preceding the subject, that is actually a good thing!  It means Hurtdidit's MailScanner antispam solution is doing its job. 

Allow me to explain.

Marketers of UCE (Unsolicited Commercial Email, or Spam) are constantly seeking new ways to increase their open rates.  Being honest about their subject lines is not terribly effective, but then spammers are not particularly burdened with the desire to market their wares honestly.

One technique they use is to "spoof" or fake the sender and/or subject line, to make it appear as if the message you are receiving is one sent by YOU.  They may use a subject which mimics a delivery error or similar.

The spammers' goals are to get you to open the message, and hopefully to click through on the links they provide.  They earn their spam sandwich bread by increasing the click-through rates, as their customers then can be provided with confirmed email addresses. 

Whenever you click a typical link within a spam message--be it in an attempt to unsubscribe or just visit their website, the links are usually encoded to call home and report your actions.  This confirms your email address as legitimate and worthy of even more spam!  What an honor, huh?

Hurtdidit's MailScanner anti-spam service works at detecting all variety of spam, and does a reasonable job at that task.  You can learn more about MailScanner's features in this article.

As mentioned in that article, there are two layers of spam scoring--definite spam is auto-deleted, possible spam is relabeled and delivered to you for review, lest you potentially lose any false-positive emails (nerd-speak for legitimate emails mistakenly flagged as spam).

Those emails which are relabeled as Possible Spam can get to be cumbersome in your inbox, however, and thus it's wise to use a Message Rule or Filter to move any such emails into a subfolder, so you do not have to wade through those messages in your inbox.

I have created a video tutorial which will show you step-by-step how to set up Message Rules in Outlook:
http://www.library.hurthelp.com/screencasts/general/message-rules/message-rules.html

To cut down on the overall spam message count, you may also be interested in my article, Basic Spam Prevention Tips.

In short, messages which have been relabeled as "possible spam" indicate a GOOD thing--it means that MailScanner is doing its job!