What really irks me about this is that I deliberately use gigantic, stupid MTAs like gmail and live mail to deliberately avoid this sort of garbage (deliberately). Those familiar with administrating large volume email can appreciate that you can perfectly configure your mail server and end up bounding all over the place because almost everyone with a mail server is not an actual email administrator and has no clue what they are doing. Email, like high school, is ultimately all about popularity . Even the least competent of email server owners will eventually get tech support to make sure google and microsoft can deliver to and receive from their Zimbra abomination. At least that's what I figured until I started getting bounces like the one below. It seems Microsoft has decided that Security Focus mailing lists are too dangerous. To step up the oddity of this policy, bounces only occur when the originating MTA is with Yahoo. I can receive email directly from securityfocus.com. I c...