On Mon, Feb 10, 2014 at 8:13 PM, Yasha Karant <[log in to unmask]> wrote:
> Our site has been edicted to Microsoft Exchange server with a Barracuda spam
> filter.  There are numerous difficulties, one of which is spam not being
> filtered and non-spam being so filtered (significant increase in mission
> critical false positives).  At present, the administrative authorities (all
> of whom appear to be management professionals, not internals nor systems
> folks) insist on Exchange, allowing open systems standards compliant
> end-users to have IMAP service.  Given this, what are the best server-side
> spam filters, either hardware or software?  "Best" should be based upon
> current field-deployed experience and/or unsolicited external reviews (not
> vendor-supported "independent" reviews).

The most effective, and one of the most efficient, spam filters is
CRM114. It's a Markovian neural net based filter, it learns very well
from users selecting what is and isn't spam, and normally deployed
each person winds up with their own tuned and quite independent
filters, so the spammers can't tune their spam to get past it like
they do with ClamAV and Spamassassin.

Unfortunately, it's not well packaged for commercial use. Barracuda
was pretty good the last time I looked, you just had to be aware of
its limitations and that it requires some ongoing tuning. And very
basic front end filtering, like activating SPF or or using SPF based
filtering in front of it, really helps reduce the load.

> Thanks for any information.
>
> Yasha Karant