Changes in the way some Hotmail messages are formatted could make legitimate emails sent using the service harder to distinguish from spam. Hotmail messages composed with alternative fonts or colours no longer feature multipart/alternative headers and are instead sent as pure HTML emails. This recent change is making life more difficult for admins fighting the spam tsunami, if Reg's reader James Masterton experience is anything to go by.
Sending MIME-encoded pure HTML is a common spammer trick to fool text-based filters. Because of this sites frequently have a server policy in place to refuse SMTP transmission of pure HTML emails. But Hotmail messages are now being sent as pure HTML, so some sites are inadvertently blocking Hotmail messages, Masterton reports.
Users are complaining, but if Microsoft relaxes the policy, then more spam is likely to make its way through. So Masterton (and many others, we suspect) is faced with a dilemma. The changes introduced by Hotmail mean many spam filtering services might need tweaking. There are so many packages, services and techniques for blocking spam (all with varying - imperfect - levels of effectiveness) that's its hard to say how big a deal this might be, but since Hotmail has such a huge user base it would appear foolish to do nothing. Alex Shipp, of email filtering specialists MessageLabs, reckons that unless changes are made more legitimate emails will be blocked.
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News source: The Reg