Software

Actually I have the solution but it runs on your own server. Very few resources needed you can piggy-back it on any file server.

GWAVA - originally designed for Netware and GroupWise but so popular it has been adapted to other platforms now.

With over 1400 messages/day my client sees less than 5 false positives per week, ands those are generally clients using Hotmail and Yahoo addresses from home.WEIGHTED heuristic scanning, Address, Keyword, RBL (including weighted RBL for less false positives), internal block list, etc. etc . etc. BY FAR the absolute best spam filter I've seen and I researched HEAVILY for 6 months.

Cost? $950.00 Canadian (About $10.00 US or a happy meal cupon). I have wieghed it against what I think is the second best system at $3000.00 (GW Guardian) and it beats it hands down at a third of the price.

http://www.beninfinite.com (How is an OUTSIDE company or service going to decide what is a false positive or not?) Plus with GWAVA, you archive messages so you can sort them and recover blocked email if needed. My client calls me and says 'joe sent an email from xxx.com and I didn't get it', I log in to their server run the archive viewer, easily find the email and send ti to their MTA for delivery. That's another bonus, the mail doesn't hit the desktop it is scanned BEFROE the PO processes it, it ties in with your Anti Virus solution and scans even ZIPs and will remove them as configured to.

I have yet to see a simpler, more accurate or cost effective solution. UNBELIEVEABLE!

We use Praetor. You can download a 30 day demo from www.cmsconnect.com. It comes with base rules which you can modify to a very high level. You can white & black list by domain or IP. You can quarantine by rules and release or redirect the mail. It runs on a public (in the DMZ) server that is the destination for our MX record. Praetor then passes the mail to our anti-virus system (on the same machine) and if the mail passes all that, it gets forwarded to our Exchange server in the private LAN. We filter out 70-80% of the incoming mail with this arrangement.

You say you want something managed externally but can be fine tuned locally. That sort of sounds like a contradiction. A service like that may charge per change, which would get expensive fast.

Take a look at www.spamhaus.org. We have just started to use it today. They are free.

We use Postini where I work. It appears to do a very good job. Check them out at www.postini.com