On Sep 19, 2007, at 1:56 PM, John K Masters wrote:
Without wishing to start a conspiracy theory but has anyone collected stats on the mail-agents used to send spam. Up till a couple of monthsago most were Outlook but since then I have seen a dramatic increase in the use of The Bat! to send spam. Obviously nothing to do with The Bat!becoming a Microsoft Trusted Partner in July this year.
I think most spam these days is sent using dedicated spam-spewing software. For that reason, I would be careful about drawing any conclusions from the agent headers. I suspect a lot of them are faked in order to get better weighting in Bayesian filters and the like. In the same vein, I sometimes see hotmail-specific headers in spam that didn't ever touch a Hotmail server.