Re: ISPmail Lenny tutorial ready
Christoph Haas wrote:
> Greylisting has been a neat hack but IMHO it was clear that spammers
> can't be kept off like that forever. Not sure whether they just try
> again. I'd assume they abuse more open relays or crack servers. Blocking
> off spammers with RBLs still seems to work best. And I'll try Domain
> Keys (DKIM) and see if that helps a little. I'm curious to see how many
> mail servers are using that.
>
> Cheers
> Christoph
DKIM is more than an anti-spam tool. Limiting it to only that is not a
correct point of view. DKIM certifies that a given mail is sent by an
approved server for the domain, and makes it so nobody else can send
using your domain. It avoids people using your domain fraudulently, and
this is why it's great! The fact that it also permits to deny some
incoming email is a nice side effect of it, but I would never say that
this is the only purpose. If everyone was using DKIM signing, there
would never be anyone using a From with a domain they don't own. That
would make the life of spammer wishing to do pishing a lot harder. A
good example could be someone trying to make a fake paypal email with
the From being @paypal.com. NO WAY it would reach my servers (not sure
if paypal is using DKIM signing though... that's just an example).
Also, remember: DKIM signing is mandatory to send to some big email
providers (like yahoo, and many others). You can use dkim signing, but
not filtering if you wish...
As for greylisting, well, I don't have statistics per say, but reading
my server's log, I can tell that it removes a part of the spam traffic.
What's good is that it does it for almost no CPU. It's like many other
antispam basic checks: it HELPS and does it's PART of the job. Note that
what does tumgreyspf is to do greylisting only if the SPF check fails or
gives no answer, which is, IMHO, a very good way of doing things.
Thomas
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