There was another thread on mailop today about email filtering. This one was about Microsoft and SmartScreen. After watching a bunch of folks make lots of comments about what SmartScreen was, and get it wrong, I waded in.
One thing that I always thought was common knowledge, but apparently isn’t, is that SmartScreen is primarily a content filter. Microsoft does use IP and domain reputation in their filtering but SmartScreen is somewhat separate from those filters.
There are other things I’ve deduced about SmartScreen over the years, through discussions with other delivery folks, marketers, and Microsoft employees as well as following press releases, public statements and reading Microsoft’s extensive help pages. Why the Microsoft help pages? Many years ago SmartScreen filters were incorporated into Exchange installations. This hasn’t been true for quite a while, but I still find the user docs a useful source of insight into Microsoft’s filters.
What have I learned?
One of the major factors in SmartScreen is specifically how users are interacting with mail.
- Recipients are acting in ways that tell Microsoft that they actively don’t want the mail in some or all of the following ways:
- marking mail a spam
- answering “yes” when Microsoft asks “did we classify this mail correctly as spam”
- answering “no” when Microsoft asks “did we classify this mail correctly as not spam.
- Recipients are acting in ways that tell Microsoft that they don’t really care about the mail in some or all of the following ways:
- never opening the mail
- deleting the mail
- never looking for the mail when delivered to spam
My professional experience is that Microsoft has the most sensitive and aggressive filters in the top 3 free mailbox providers. I’m not convinced that this is intentional. But whether to not it’s intentional doesn’t matter. It’s their system and, in general, we senders have to deal with it. The good news is that there are MS employees willing to listen and talk to senders. It’s unclear to me how much of those discussions are shared with the development teams and are influencing how the filters are evolving. But I know there are discussions.
While it sounds like I’m dissing Microsoft here, I don’t think the delivery issues are wholly their fault. Many senders with Microsoft delivery problems have underlying issues that need to be addressed to get into Microsoft. But they see Microsoft’s sensitive and aggressive filters as “unfair” and “broken” because they aren’t having problems with other free mailbox providers. They refuse to change what they’re doing and thus see no change in their delivery.
I do think inboxing is a moving target and it’s hard for some types of senders to crack.
I do think machine learning filters are diverging at the different ISPs.
I do think that responsible senders who actually pay attention to their data collection process mostly have fewer delivery problems.
I do think that sometimes the filters are a little bit out of line and do things even the developers don’t expect.
I do think it’s all really complex.
I do think most mail gets delivered correctly, even if there are some spectacular mis-deliveries.