Sendmail: How does one blacklist annoying spammers?

[Craig White]

On Sun, 2010-06-27 at 20:09 +0930, Tim wrote:
> On Sat, 2010-06-26 at 17:55 -0700, Craig White wrote:
> > I use greylisting on all mail servers that I administrate and I
> > specifically use one that maintains a list of well known smtp servers
> > such as yahoo - it's a rather substantial list and maintained so that
> > pretty much obviates your point #1.
> > 
>            (fussy servers)
> 
> > Point number 2 is well taken but in my experience, there aren't that
> > many times this has come up (only once) and yes, that will cause an
> > issue but again, I am able to whitelist the range of servers from that
> > system.
> > 
>            (multi-rejects)
> 
> The trouble with those problems is *having* to do something about them,
> for something that should really manage itself (servers retrying to send
> to a supposedly busy server, or whatever other reason for a try later
> response).  Or, more to the point, knowing that you have to do so, in
> the first place.  Alright if you do so, but a problem if you don't, or
> you're one of those people who think that all collateral damage incurred
> when rejecting spam is acceptable.  Especially so if you're trying to
> mail someone, and something out of your control is getting in the way.
> 
> In theory, it's a clever technique.  In practice, like all anti-spam
> techniques, there are flies in the ointment.  I don't mind people
> suggesting it, or implementing it well.  But it should be advised with
> the appropriate precautions that you will need to manually add some
> overrides.  And unless you monitor logs (many won't), or hear about
> problems in some other way (and many won't), you aren't going to know
> that mail isn't getting through.
> 
> I don't hold with the contention that people should simply put up with
> email being inordinately delayed because it doesn't have to be instant.
> A few minutes isn't usually too much of a problem, but occasionally is,
> and anything more than a few seconds for an email to whiz around the
> world, in this modern era of fast computing, isn't really excusable.
> Mail taking hours is unacceptable.
> 
> Having to change to another messaging format to overcome this isn't an
> appropriate solution.  There are plenty of cases where someone needs to
> be sent something in writing, so the phone isn't appropriate, and
> instant messaging tiny notes back and forth isn't, either.
----
10 different mail servers and have used greylisting for more than 5
years and only whitelisted a few named mail servers for one company to
whitelist a group of servers whose outbound mail queue could change the
sending server one time is hardly what I would call collateral damage
but you are so determined to make your weak point which I already
conceded but I know it is of little to no consequence.

Specifically, the whitelisted servers were all from a company that
actually does supposedly opt-in mail spamming and this customer of mine
was using them and it was slowing up their 'proofs' before they
unleashed on their mail list.

I have seen nothing in e-mail whose computing cost compared against spam
control has even come close to matching greylisting and while I can see
it would create problems for an ISP, corporate mail servers should not
live without greylisting.

Craig



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