On Tue, 2011-03-01 at 22:06 +0100, Karl Fischer wrote: > I'm using exim for many years now and over time I have developed a > - more or less - complex set of filtering rules to prevent SPAM. > > One of my main assumptions is that legitimate mail servers do (should) > have proper forward and reverse DNS records - however, that's not > always the case.
No its not. The UK police suffered from this problem caused by the behaviour of their contractor Cable & Wireless. That has now been successfully solved with valid HELO names. They use Exim. The British heath service (NHS) also issues bogus HELO names. Unsurprisingly the contractor is again Cable & Wireless. A small example of organisations unable or unwilling to use resolving HELO names can be found on sys.u226.com/t21/t21.php There are a lot of computer 'experts' who don't have a clue how to get their mail servers' HELO names to resolve. These days even the clueless pronounce themselves to be 'computer experts'. Ebay, Micro$oft, Paypal, Facebook and British Telecommunications can not always get their HELOs correct. Google does, every time. If you are interested I'll email you my ACLs which test for non-compliance with our 'standards'. -- With best regards, Paul. England, EU. -- ## List details at http://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
