Re: [Exim] variation on dns blacklists

On Mon, 12 Jan 2004, James P. Roberts wrote:

> There are a lot of "email forwarding for life" services provided by
> colleges and universities, and I suspect the number of these will
> grow over time.

There's something in what you say; but if they serve primarily as
spam-laundering services, then it's not going to work. (By assisting
them, we could be making ourselves accessories to what in the UK is
now a criminal offence. IANAL and that was not legal advice, which I
am not qualified to offer.)

Overall, we quite some time back passed the point of 70% of mail
offerings being spam, and that's not counting the ones that we refused
to even talk SMTP to. That's more than two out of every three mail
offerings being spam. [Indeed on one of my remote accounts, I was
finally getting way above 300 spams for every 1 productive mail,
before I gave up on it. There would be at least 100 spams a day on
that account, sometimes more; and perhaps 1 or 2 productive mails a
week, sometimes less.]

Anyway, back to our Department: the current major route for spams to
get past our far-from-fascist defences is by getting them laundered
and forwarded via user accounts elsewhere.

> The institutions that provide these services tend to *not* do any
> filtering. It is a deliberate decision, based on the idea that even
> one false positive is too many, for such a service.

I think it's fair to comment that such absolutist principles are all
very well in theory, but reality demands a compromise solution.

> I believe, given their large number of very diverse customers, that
> they are correct in this approach. As a customer of such a service,
> I am happy to know that they are not blocking anything, since I can
> then sort through and block what I want on my end, or not.

We can arrange that, if individual users want it; but the overall
verdict from our users is better than mere toleration of what the mail
admins are doing for them: significantly more users have commended us
for our anti-spam policies than have complained about them, and quite
a few send us copies of anything that leaked through so that we can
tune the blocking rules. Working as I do in a job where almost
everyone who appears at the office door is there because they want to
complain about something, I take that as praise indeed. ;-)

> My preferred solution would be to migrate to a different mail box
> format, so I can divert the email to each customer's "spam" folder,
> and let *them* do any looking for false positives. This will work
> nicely with IMAP service, I think.

Yup, that works fine (see earlier postings from myself in relation to
our Department, and from the campus central postmaster, Chris, about
the various strategies used). You don't (necessarily) need a
different "mailbox format", you just need an imap server that supports
the mailbox format which you use. Which is not to say that there
aren't tradeoffs to be made from a choice of mailbox format, but it
seems you're concentrating on the wrong issue of detail - It's IMAP
versus (presumably?) POP that's the issue here, not one mailbox format
versus another.

best regards