Re: [exim] Defer as a spam filter

On Fri, 4 Mar 2005, Tom Kistner wrote:

> It all depends on how you can afford to push a policy that is
> uncomfortable for your users.

In my case, I push it relatively hard.

We gained approval from senior management to implement "appropriate
measures" to reduce unsolicited mail "in accordance with best practice
within the academic community and current legislation" ... "the committee
recognises that there is a possible risk that this action may result in
legitimate email being rejected".

My wide interpretation of this is that I can implement techniques that
enforce proper compliance to RFCs, spam scoring, DNSBL rejections, syntax
checking, attachment filename/type restrictions, and various other
methods, if they help to reduce spam.

Of course, some of these measures cause 'legitimate' mail to be rejected
as well; we issue an address they can query things with, and I take the
time to explain the problem and possible solutions, and if necessary why
such measures are implemented. If I didn't want to do that, I'd probably
have to relax the rules.

I do think times have moved on and I need to be more proactive about
providing information about what techniques we use, why, and the possible
consequences. But as far as I'm concerned, I have management backing, and
I don't mind taking flak from someone who (quite reasonably, since they
are rarely an experienced 'mail admin' type) doesn't understand why my
mail system is so anal and pernickety (in their view). See the comment
from qmail admin mentioned yesterday here about retarded Exim. I agree
that in many corporate environments, and cases like Tom's, this would all
be trickier.

It's very much down to the culture of the organisation/customers/employees
as to what you can get away with. Sometimes, though, it is necessary to
manage (or massage) expectations so you can use some trick to help them in
the long run - greylisting could probably be counted here, as could use of
certain DNSBLs I guess.

And like Alan, it doesn't matter what I do, I always get a trickle of
complaints about XYX spam got through, and a trickle that such-and-such
messages was rejected. Just gotta accept that no system is perfect and
get on with it.

I keep thinking we should have a "no mail checking day", when I turn off
all DNSBLs, syntax checking, spam scoring, etc, and just let it all flow
through. And let them see how much we're protecting them from - in
generally, they just haven't got a clue how much nasty stuff aimed at them
they never see.

Jethro.

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Jethro R Binks
Computing Officer, IT Services
University Of Strathclyde, Glasgow, UK