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Taking a Closer Look at the New Hotmail Filters

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by: Robert Consoli (@IBMforMarketing)
18 August 2010

In my prior post, “New Changes in Hotmail: What Every Marketer Should Know,” I promised to share more about what I believe is a huge update from Microsoft: the newest implementation of its SmartScreen spam-filtering technology.

SmartScreen has been around for a while, but the acknowledgement of its uses and capabilities can help marketers better understand how messages are filtered.

In its video, “Microsoft SPAM-Fighting Technology in Hotmail,” Microsoft discusses “gray mail,” which it defines as mail that isn’t being indiscriminately sent; there’s a reason for it. This could be, for example, a newsletter or marketing promotion that the user is getting because he or she has signed up at the website.

Microsoft has been grappling for some time with the problem of unwanted email getting through its filters. It even has an acronym for it: “SITI” (pronounced “city”), which stands for Spam in the Inbox. The new implementation of SmartScreen is designed to head off and significantly reduce SITI.

SmartScreen is mainly based on heuristics and machine learning. One of its strengths is in weighing both the content and headers of a message for “spam-like” content and design.    

The SmartScreen technology’s first level of filtering, called connection-level filtering, takes place at the router level. At connection-level filtering, Microsoft takes one of three actions: accept, reject or place in a space Microsoft calls the middle ground. Microsoft places senders that it does not know enough about yet in the middle ground. To learn more about these senders, Microsoft accepts a limited amount of email and gauges user reaction to determine a sender’s appropriate reputation and level of content filtering. This applies directly to what many marketers have already been doing with the Hotmail “ramp up,” which Microsoft requires so that the SmartScreen filters can learn from an emailer’s sending patterns and user engagement levels. Based on the sender’s performance, Microsoft determines the volume of messages it is willing to accept and how it will be delivered (inbox or bulk folder).

Content filtering is also an important part of the SmartScreen filter. Some aspects it looks for to determine delivery are:

  • The presence of authenticated sending domains
  • Composition of content, e.g., image-to-text ratio and type of message that was sent

Other criteria that the SmartScreen filter uses to determine delivery are user preferences, such as which senders have been placed on block and safe lists, and other actions, such as whether a user has clicked the junk button (a measure of user engagement).

Microsoft states very clearly that it wants to understand, not only who the sender is but who the receiver is.  It wants to understand the sender’s relationship with the user, what types of messages are being sent and how the user is reacting to those messages.  For example, if a user has deleted 10 messages from a sender, Microsoft could prompt that person to unsubscribe from all future messages by using its Auto Unsubscribe feature. This feature existed in the past but only on an individual email basis. It primarily works based on a list-unsubscribe header that the sending servers must place in the header. In cases where the sender reputation is good, and the Auto Unsubscribe is present, Microsoft will offer recipients the option to opt out of all future messages. However, in cases where Microsoft believes a sender would not honor its opt out, it will proactively block that sender’s future messages to any user who marks the messages as junk, which in turn will place a negative mark on the sender’s reputation at Hotmail.

The end result is that Microsoft wants to give its users more control over their inboxes. In turn, this means that as marketers, you will need to focus more than ever on:

  • User Engagement
  • Authentication
  • Auto Unsubscribe
  • Domain/Brand Recognition
  • Relevance
  • Getting Added to Recipients’ Address Books

For more information on Microsoft’s SmartScreen filtering technology, you can visit:

What’s new in Hotmail


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