On Wed, 19 Mar 2003, Justin Mason wrote:
For example, until last week, I was using an ISP that did not have rDNS
for their outgoing SMTP servers. Now *I* know the importance of rDNS for
SMTP servers etc., but I was just a user. My 3 support requests didn't
count for much, and as far as I know the servers still have no rDNS.
That is the purpose of a group such as this - to establish standards
expected for effective inter-operation. If your ISP does not adhere
to *current* established standards, why would any additional changes
be any more effective.
The stock response to this is "well, change ISP" -- but that's a naive
view of most of the world, where the choice is not available. In my case
(in Ireland), accessing the net through this ISP was 2/3 the price of its
nearest competitor.
Complaining is not working? Do they even answer your requests?
I'm sure that you are aware that paying them rewards them for
not following standard practices.
Also, requiring rDNS is not even that effective a test; our rule for this
condition in SpamAssassin gets this rate:
35.5901 3.0576 0.921 0.78 1.33 NO_DNS_FOR_FROM
in other words 35.59% of spam has no rDNS, but 3.05% of ALL nonspam mail
does too. The latter is bad news, it's a *very* high false positive rate.
Spam outfits have a habit of targeting secondary mail servers
(higher MX value). By just introducing rDNS checks on our
secondary mail server, we cut down on a huge amount of wasted
connections.
---
John Johnson - System Administrator; Sirius Systems Group
jjohn(_at_)sirinet(_dot_)net KJ5AA
(580) 355-6436
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