[plug] OT Any ISPs allow intelligent Spam filtering?

[Daniel]

Hi Gavin and Plug, excellent explanation - thank you.
Back to the drawing board on filtering my own mail (I'll draft a question 
for plug)
Regards,
Daniel.

At 08:28 4/01/2002 +0800, Gavin Rogers wrote:
>On Thu, 3 Jan 2002, Daniel wrote:
> >.. snip ... 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/