[AusNOG] Mail Filtering + ISPs
josephb at gmail.com
Sat Feb 17 13:25:49 EST 2007
> I've actually found it stupidly easily to get badmarked by SBRS, ISTR I had 1
> spam run go out for less than 1 day and managed to tip my score over and
> be blocked by iiNet before. (said spam run from dodgy web scripts on
> public web servers)
No solution is perfect, the SBRS score is built on the fact that most
of the IronPorts in the world report back to Senderbase with stats on
mail volume, spam content rating and other info.
Senderbase then uses this information plus a bunch of other metrics to
build a SBRS score between -10 and +10.
IronPorts around the world who have never seen a connection from you
before, are able to get an idea on what mail from you is going to
look like and apply the appropriate level of filtering/limiting.
It isn't easy to have a bad SBRS score over a long period of time,
I've always found it usually involves sending spam one way or another
The good part about most IronPort installations is they are left
alone, fully automatic to do their thing and if you start sending
clean mail the IronPorts around the world report back to Sender Base,
over 12 to 24 hours the SBRS score will start to change and reflect
that you are now sending clean mail.
With regards to mail forwards, especially catch alls, in this day and
age they result in too much spam being received by the end mailbox.
A number of big hosting companies in the US have started disabling
catchalls, or at least limiting their use so that they can only be
forwarded to email providers like Gmail etc.
Some hosting providers also use specific servers or IP addresses to
handle outgoing forwards, with the understanding these will be
blacklisted from time to time however normal outgoing email won't be
Personally I think providers should be doing all they can to NOT
forward on spam to external mail boxes, in the long term it will only
result in pain.
All IMHO :)
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