There is another thread on another forum that has gotten rather heated regarding the topic of Outlook.com and how contacts are handled. Since I believe the individual who is upset would really like to know more, but is not aware about the usual behavior of "contact harvesting" from all received and sent e-mail, whether one puts said addresses into one's own personal contacts (or even has removed them from one's own personal contacts) I thought I'd start a thread here, in the appropriate place.
Very few people realize that most web-based e-mail interfaces have a "contact harvesting" feature. Every e-mail you receive or sent has it's respective "From:" or "To:" address harvested to a contacts pool most people generally never see or know exists unless they seek it out to purge it. You can even have added and deleted a contact from your personal contacts but this will not result in its removal from the "harvested contacts pool" unless you also explicitly go there and purge it. The "harvested contacts pool" is pulled from, in addition to your own personal contacts, when you start typing an e-mail address to create the dropdown list of possible addresses that matches what you've typed so far.
I am going to use some screen shots from one of my Gmail accounts to illustrate what I'm talking about. Stuff that could be considered personal to specific individuals who are in my "harvested contacts pool", which Gmail calls its Other Contacts category has been redacted. I will stick with business contacts from my personal groupings since these addresses are for businesses that share their e-mail addresses via a number of public media.
For some reason I don't have any of the capability to attach images at the moment. I'll try posting this and seeing if I can follow on with what I'd intended to add next.