Why would anyone tolerate this?
There are plenty of good freeware email clients out there. I have to use Outlook at work, but have never used any MS product for email personally. We're all bombarded with enough pointless, soul-killing advertising daily. And does anyone actually buy any of the services or products offered? Or is the revenue just from 'delivered' ads?
I suspect the only people that would use the 'free' MS email client are those that just don't know any better.