How Microsoft develops Outlook's spam filter


Tuesday, July 06, 2010

Each day, I discover emails in the Outlook junk mail folder that do not belong in the junk mail. Sometimes I really wonder on what criteria Microsoft decides an email is spam or junk. Today, I discovered that suddenly an email from (an excellent website by the way) got classified as junk. I have been receiving emails from for years without problems. So, my typical reaction is to mark the email as safe sender and move it to my Inbox.
Now, I'm starting to think that Microsoft utilizes a very clever algorithm for filtering emails. Everyday it randomly flags some emails as junk. It counts on the user for inspecting the junk folder and whitelisting the emails that are not spam. This way, all Microsoft has to do is accept all emails in the whitelist the user created and further randomly move some emails to the junk folder. Eventually, when Microsoft classifies enough random emails as spam and the user persists building the whitelist, there is hope that one day the Microsoft Outlook email filter will work as expected. Now, don't tell me Microsoft isn't innovative!

Bruno Fierens


This blog post has received 4 comments.

1. Wednesday, July 07, 2010 at 2:20:29 PM

Outlook''s spam filter is completely useless in my opinion. Not only does it seem to filter at random and ineffectively, but it also by default displays a popup modal dialog saying "I caught some spam, wanna see it?" every time it filters a message. In effect making spam more intrusive than non-spam. Of course it seems that it is more likely what it thought was spam was actually legitimate email, and what it thought was legitimate email was really spam, so it is probably a good idea that it provides more notification on spam messages.

Jim McKeeth

2. Wednesday, July 07, 2010 at 11:14:38 PM

The Thunderbird junk filter, on the other hand, is excellent. It gets rid of perhaps 90% of my spam, with very few false positives.

Rob McDonell

3. Friday, August 06, 2010 at 3:56:14 AM

I''ve often thought this.. what *really* annoys me is that it doesn''t expose anything about why it moved a mail to junk!

Phillips Richard

4. Wednesday, September 01, 2010 at 7:24:12 AM

Glad I switched to The-Bat! and Antispamsnipper a couple of years ago!

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