Managing personal Outlook.com account settings, security, and privacy
MORE INFORMATION
When viewing your Recent Activity page, the link at the top of the page, called "Learn more about the recent activity page", redirects to "What is the recent activity page?" There you will find details regarding specifics "about when and where you've used your Microsoft account within the last 30 days". Primary to this particular thread about Automatic sync is the section: "What are the different session types?"
At no time does that section mention "Automatic sync". The closest reference would be found under Email protocols, in which the following is presented (see image). Exchange ActiveSync and Internet Message Active Protocol (IMAP) imply to me that IP addresses from Thailand, Indonesia, China, Brazil, and similar disreputable countries are using the ability of "apps and services which manage emails" to sign you in automatically.
This is a serious weakness in internet security. A possible, short-term protection may be to: uncheck all references to "remember me" or "keep me logged in" and to make certain that your Temporary Internet File folder is emptied each time you close your browser.