On 02/10/2014 10:40 PM, Nico Kadel-Garcia wrote:
On Mon, Feb 10, 2014 at 8:13 PM, Yasha Karant <ykar...@csusb.edu> 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.
Back when I ran a Barracuda, I found my most effective plan was to
automatically 'quarantine' any message from a mail server without a
reverse DNS record and set a fairly low quarantine threshold for
everything else. Short of viruses, I didn't delete any email automatically.
Once it was trained, I loved it - but that took a few weeks and oodles
of time.
Pat
--
Pat Riehecky
Scientific Linux developer
http://www.scientificlinux.org/
