better blocking at MTA level (off-topic)

[Jason Ede]

The problem with greylisting as we found when we enabled it was that some MTA's treat a temporary reject code (450) as a permanent reject code (550) and our customer was complaining that they weren't getting email. Whilst we could exempt every MTA they flag up to us from greylisting checking there is no way to prevent email from an unknown source getting blocked and not getting through to them. Until we can resolve the problem without telling our customer to tell anyone emailing them with problems to get their MTA fixed it unfortunately has to be off... It did vastly reduce the load on our server whilst greylisting was active though.
 
The hit of the first email being delayed for the 5 minutes we initially chose was insignificant and no-one would really notice... 
 
Jason

________________________________

From: mailscanner-bounces at lists.mailscanner.info on behalf of Sergio Rabellino
Sent: Sat 26/05/2007 12:03
To: MailScanner discussion
Subject: Re: better blocking at MTA level (off-topic)



I'm very happy about greylisting.
I introduced it (smf grey -sendmail filter) one week ago and the spam
shrinks by 90%.
Obviously we could/would pay the delay of the "first" email against the very
high reduction of the spam.
Also my server runqueue goes from "uptime 8" to "uptime 0.6", more cpu for
other  jobs....

Bye.
----- Original Message -----
From: "Koopmann, Jan-Peter" <jan-peter at koopmann.eu>
To: "MailScanner discussion" <mailscanner at lists.mailscanner.info>
Sent: Saturday, May 26, 2007 10:17 AM
Subject: better blocking at MTA level (off-topic)


Hi,

looking at todays 88% High Scoring Spam ratio I would like to block more
at the MTA level. What are relyable RBL services (commercial is fine)
that can be used? Or other methods besides tarpitting, pipelining tricks
etc. at MTA level (which we all do) that would reduce the load?

Or am I the only one suffering from massive attacks the past few days?
What are you guys using?



Kind regards

Jan-Peter Koopmann

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