Hi > need advice about greylisting practices. Here's the scenario: > - sender at example1.com sends automatic emails using the MTA > infrastructure of his provider > - recipient at example2.com greylists provider's IP_1 > - provider retries from IP_2 which gets greylisted too, again.
You have to look at the goal of greylisting. The goal is to filter out unwanted traffic sent by drones / trojans without proper queuing. A proper MTA will have queueing and in case of a temporary failure at the destination, re-attempt delivery after a while. If this happens, most greylising implementation I know will allow traffic from the same from username and ip for some time and refresh that time on each email. Because some sender do such strange things as using multiple sending ip addresses some consider a /24 IPv4 or /64 IPv6 to be the same sending IP. > Tried to dig into RFC6647. Chapter 4.1 describes 'Unintended Mail > Delivery Failures', in particular "although example.com has sought to > improve its email throughput by having two servers, it has, in fact, > amplified the problem of legitimate mail delay introduced by > greylisting.". Considering MTA cluster of sender's provider with 4k IPv4 > and 2^80 IPv6, the issue grows. WHY would somebody in their right mind use a cluster of IP addresses for sending emails from the same source / customer? Use ONE ip address. > The provider recommends "adjusting anti-spam/greylisting configuration > to properly handle messages sent from rotating IP addresses". And I have > no clue what does he mean by that. Why would a sender in their right mind - if not trying to dodge blacklisting because he is sending spam - rotate sending IP addresses? Use ONE ip address! At least ONE ip address per customer so if one of your customer is sending spam he is being punished. Let your one sending IP address grow a good reputation with recipients and antispam services. Mit freundlichen Grüssen -Benoît Panizzon- -- I m p r o W a r e A G - Leiter Commerce Kunden ______________________________________________________ Zurlindenstrasse 29 Tel +41 61 826 93 00 CH-4133 Pratteln Fax +41 61 826 93 01 Schweiz Web http://www.imp.ch ______________________________________________________ _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
