akismet – can it scan existing blogs

I am having problems with google webmaster and one of the suggestions given to me was to install askimet as it will stop oa lot of the problems that I am experiencing.
I have paid for and installed askimet but their site doesn’t state if it can check already published blogs and bb forums. There is no customer support to submit questions like this on askimet. Does anyone know if askimet scans existing blogs? If it doesn’t scan existing blogs how can you submit them to get them scanned without deleting them from the blog?