I use Mailwasher Pro and i,m getting duplicated Spam as well.
Not from all, just from some.
The most persistent spam comes through Chinanet and Hanaro.
Although i do bounce spam back [a dubious idea and it creates more crap ] i report all spam through spamcop, if it does any good , who knows.
Ive tried setting up filter after filter, but still even small amounts get through, and even tho i like outlook express, and i dont like web based mail servers, it really is the biggest thorn in the side of the inet.