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Bill Horne wrote: > Checking for PTR records is routine for most ISP's... I'm referring to not just checking for the presence of a PTR record, but applying a regular expression to the format of the returned PTR record. This I consider arbitrary, and highly error prone. The idea of tracking blocks of dynamic IP addresses is also tenuous (unless the ISPs themselves participate in the system), but a step more reliable than making judgments on the appearance of the PTR record. > ...and I'm surprised that you haven't gotten rejections more often. Pretty much never...though of course many spam rejections don't generate a bounce. > Of course, it's imperfect - effectively, just a confirmation that the > machine sending the mail is not a desktop - but it's all we've got. This classic web page provides a good rant on why most anti-spam techniques are fundamentally broken: No anti-UBM measure for SMTP-based Internet mail works http://homepages.tesco.net./~J.deBoynePollard/FGA/smtp-anti-ubm-dont-work.html It has a section specifically on the above issue titled "Treating other ISPs' customers as third-class citizens." As a community who frequently chooses to operate our own servers, we should be doing our part to discourage these types of broad based and misguided anti-spam measures. -Tom -- Tom Metro Venture Logic, Newton, MA, USA "Enterprise solutions through open source." Professional Profile: http://tmetro.venturelogic.com/ -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _______________________________________________ Discuss mailing list [hidden email] http://lists.blu.org/mailman/listinfo/discuss
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