Mate if your going through 800 then i'm guessing your reading through lots of "other" peoples mail files.. Rather than doing that, let them do it.
I've built a mail template that allows users to work out whats real and not, they then set it as mailgood or mailspam.
As an admin all you do is check the list occasionally, i've built a bunch of views that let you see domains etc at a high level, makes it easier to track down.
You can read more about my template mods here http://www.taet.com.au/mb.nsf/plinks/MSMH-5ZSCWT
Also some other people are doing some cool things like emailing the users a newsletter with the captured email etc..
Matt