https://www.siliconvalley.com/2019/04/15/microsoft-breach-exposed-hotmail-outlook-email-users/

Users of Microsoft’s Outlook, Hotmail and MSN email services had their accounts exposed for nearly three months after hackers gained unauthorized access via an Outlook customer support account.

Microsoft said the breach, which occurred between January and March, let hackers view individuals’ personal information such as message recipients and email subject lines. The software giant didn’t disclose how many email users had their accounts exposed; officials said that the hackers, whom Microsoft called “bad actors,” were unable to get access to the email information of the majority of the accounts that were compromised.