Hotmail's fight against spam has certainly come a long way in the last five years. Over the last several years we've made substantial investments in the research and development of sophisticated anti-spam technologies. SmartScreen is the collective name we use for a cloud-based set of technologies and algorithms that leverage machine learning and artificial intelligence to assign a “spam probability” score to each incoming message. This enables us to filter out over 98% of the spam sent to Hotmail inboxes, blocking 5.5 billion spam messages per day.  Microsoft utilizes SmartScreen across Hotmail, Microsoft Exchange, and Microsoft Forefront, bringing consumers the benefit of business-grade spam protection on Hotmail.

With the soon-to-be-released new version of Hotmail, we’ve added a number of innovative new spam fighting technologies that will further reduce the amount of spam in your Hotmail inbox. Here's a short video featuring myself, Dick Craddock, and John Scarrow telling you a bit about how Hotmail's latest innovations help bring you the best spam fighting on the web.


Hotmail’s latest innovations in fighting spam

New spam-fighting innovations include:

  • More advanced IP and content filtering – Hotmail receives over 8 billion messages per day, giving us 8 billion input variables to work with and learn from. Each message we receive further informs SmartScreen’s IP filtering algorithms, making SmartScreen even “smarter.” Because Hotmail is the largest webmail service in the world, it also receives more telemetry on bad IPs than most any other service – either directly or through third parties. This gives our spam filters more opportunity to inform their artificial intelligence than pretty much any other service.
  • Spammer infrastructure detection and destruction – SmartScreen not only blocks spam, it uses “x-ray vision” to see behind the URLs contained in malicious email to the source URLs, which we can then block along with their IPs. This means spammers have to abandon their current infrastructure and pay for new places to hide out. By making it more expensive to continue their business, we are taking away their economic incentive.
  • Time-traveling filters – We can't always identify a new spammer the moment they start sending spam. But once we identify one, we can go back and clean out spam that they’ve already sent to your inbox before you ever see it. We call this a time-traveling filter, because in some sense we are able to go back in time and get rid of the spam even after it's been delivered!
  • Personalized spam filtering – One person’s junk mail is another’s desired piece of mail.  Using artificial intelligence, Hotmail personalizes spam filtering according to the individual preferences of each of the 360+ million customers who use Hotmail, reducing false positives while improving effectiveness at the same time.
  • Tagging – Hotmail tags each message you receive, whether in your inbox or in the Junk folder, to help you understand little bit more about why the message was categorized as it was. For example, if you previously marked messages from a sender as junk, we'll tell you that, or if you use a client email program with Hotmail, we'll tell you when that program has rules that result in moving a particular message to another folder. This gives you more direct control of spam management in your inbox unlike any other service.

Krish Vitaldevara
Senior Program Manager, Windows Live Hotmail