twitter's Journal: Microsoft Hotmail's Spam Block Failured Documented.

Guy Kewney documents the sad state of spam blocking by Hotmail. The "Contact Status" is broken, mail with obvious spam keywords end up in his box, offers from known spammers come through but legitimate mail is blocked from entire domains. Undoing a domain block will cost you lots of money but may never work because M$ plays favorites with what email client is used by the sender.

he wanted to fix it. Hotmail support "would not tell me why my domain was being flagged for spam, and when asked what the possible solutions were I was told I could sign up for 3rd party accreditation through Sender Score Certified (at a cost of $400USD start up, and $1000USD each year) who maintain the only whitelist service Hotmail use, and was also advised I could try tightening my SPF policy. [Tightening the SPF policy did not work.]

SenderID technology which Microsoft had championed (and Hotmail use) as another anti spam technology was in fact highly incompatible with SPF policies. [and they knew it]

[Researcher Dominic Ryan says] "I can send to Hotmail without a problem using Outlook 2003, but no cigar with Mozilla Thunderbird. I think that this suggests that the headers the email clients add to an email also play a crucial role in determining if the mail gets through or not."

The result for the end user is email that's unreliable, filled with junk, and disspears if you go on vacation. The author doubts pay to send schemes will fix the problems.

The part about picking email client favorites is disturbing but par for the M$ course. When they can't make a better piece of software, they break the competitor.