[plug] OT Any ISPs allow intelligent Spam filtering?

[Gavin Rogers]

On Thu, 3 Jan 2002, Daniel wrote:

> Hi Plug,
> I'm sorry my understanding is still badly lacking on this spam filtering
> business.
> I considered forwarding my mail to a free service with a good spam filter
> but I couldn't find one that was above the basic level.
> I've looked at a few spam filtering mechanisms, but I am reluctant to have
> a permanent connection just to filter spam - can anyone tell me of an isp
> that offers a comprehensive spam filtering service (like those below)?

Hello Daniel,

Very few ISPs will filter spam as a general rule. If mail bombed by one
source, then, of course, all ISPs will block the offender, but your
average every-day spam usually is left be and ISPs aren't willing to
change this anytime soon.

One reason is that of performance. ISPs get a lot of email :-) Spam
filtering and/or virus scanning every email would just kill performance.
That leads to angry support calls. Anyone who has ever worked in a call
centre can agree with me here - those sorts of calls are the worst kind!

Even for the small email installation we have at work, servicing about 70
users, we receive about 3000 emails a day. exim + exiscan + mcafee + a few
spam rules takes about 3 seconds of time on a Celeron 266 (on average) to
scan each email. That's 150 minutes/day that our email server uses up
scanning for viruses and spam.

Take an ISP, with 5000 users. Every user, every day, receives 5 emails
(say). That's 25,000 * 3 seconds = about 20 hours. Ouch. Large ISPs can
hardly write the received emails to disk fast enough without also having
to process them...

The other sticky problem is that of liability. For your home and family
email, it probably doesn't matter a great deal if a bit of spam got
through or worse, a legit email was killed off as spam accidentally. For
an ISP, they just can't do this! Customers would complain about receiving
spam on their 'filtered' service, and customers would start threatening
with legal nastiness if an email was ever deleted that shouldn't have.

So, ISPs leave their customer's email alone and recommend they use virus
scanning and spam filters of their own. Some have a @staff.isp.com.au
sub-domain for staff email which is checked. I guess the ISP feels happy
being resposibile for their own email...



---
Gavin Rogers                    |    Amateur radio station VK6HGR
grogers at vk6hgr.echidna.id.au    |    http://vk6hgr.echidna.id.au:800/