On the WIN VPS you can change the mailenable config to use RBLs that will assist some, you can add spamhaus and spamhaus xbl and it will cut a good 20% of spam off and also save bandwidth by disallowing connections, you may also consider using Spamcop as a RBL and it will further cut the amount of spam by as much as 50% but it has more false positives that won’t allow some legit mail in at times.
Some mouse clicks are out of order and possibly some spelling errors. I will be making some edits to correct them, but you can get the point with this.