DCC a success at the University of Manitoba

Tim Wicinski tim@meer.net
Mon Mar 31 00:22:16 UTC 2003


We haven't started the public whitelisting, but I like your shared 
whitelist idea. I think that even ISPs could do this and have some 
sensible actions.

We're still seeing issue with the rejection levels for short messages. 
I've been gathering my few/notmany/many stats, but even with notmany set 
to 20, it doesn't flag that many.  It's odd.

DCC is rejecting 60% of our spam. We add RBL+ and a dialup RBL as well 
as local blacklists to catch the rest of them.

Gary Mills wrote:
> It was just a week ago that I finally enabled DCC rejection on the U
> of M central mail servers.  There are two of these, with about 25 000
> users, including students and employees.  Both run sendmail with DCC
> running as a milter.  The rejection limit is set at 100.  All campus
> IP addresses are whitelisted.  Users can also contribute to a central
> whitelist through a web application.  This web application also allows
> them to view a summary of their rejected bulk mail for the past week,
> and to view the DCC log files for those messages.
> The response has been quite enthusiastic.  One user reported that his
> spam load dropped from 30-100 a day down to 3 a day.  We've had many
> similar reports, although most were not that dramatic.  Comparing DCC
> rejections to total mail deliveries shows about 30% rejection, which is
> quite impressive.  The mail queue dropped from 50 000 to 15 000, over
> a period of five days.  Most of this mail was either spam that was
> addressed to over-quota mailboxes, or automatic responses to spam that
> could not be delivered.  Keeping the spam out made quite a significant
> reduction in the load on the mail server, too.
> In general, the central whitelist works pretty well.  Users cooperate
> in building this whitelist, which has about 1000 entries now.  The
> advantage of this approach is that only one recipient has to whitelist
> a source of legitimate bulk mail to make it available to all.  That is
> also a disadvantage, of course, but it's a minor one.  We didn't want
> to require each user to maintain his or her individual whitelist.
> I'm using `pubcookie', an implimentation of WebISO, to authenticate
> users who wish to access the central whitelist web application.  This
> works pretty well, although it does add another layer of complexity.
> The application itself is just a perl script, using the CGI perl
> library.
> We have heard from some people who are concerned about losing mail
> because of DCC.  The most common case would be conference announcements,
> which often are a true `one time mailing'.  I can't offer them much
> in the way of a solution, other than to remind them that their e-mail
> is usable again, now that the spam is gone, and that the conference
> announcement mail will be returned to the sender, rather than being
> simply discarded.  Return receipts have also been a problem, because
> people often don't realize that they are even using them.  They don't
> understand what is happening when DCC rejects them.
> There is also some disagreement about what constitutes spam.  Some people
> seem to be somewhat accepting of spam.  A few even whitelist offers for
> breast enlargement products and free on-line casinos.  Others are quite
> outraged at even a small amout of spam.  They say that it's clearly spam,
> and that we should be able to block it.  Some people also were getting
> large amounts of spam, whereas others were getting none at all.  This
> difference seems to depend on how long their e-mail address has been
> publically available.
> I still get some spam, mainly that notorious MIME/HTML spam with very
> little content.  All in all, though, I'm very pleased with DCC, and
> I'm grateful to Vernon for all his work on it.

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