After sending a group email via Thunderbird I get a return email from "The Outlook.com Team" as follows:- Hello Hotmail User, We noticed some unusual activity in your Outlook.com account. To help protect you, we've temporarily blocked your account. Why are you seeing this? Someone may have used your account to send out a lot of junk emails or something else that violates our Terms of Service. How can you unblock your account? The fastest way to unblock your Outlook.com account is to verify your account. If you haven't setup a mobile phone in your account, please contact Customer Support. Thanks, The Outlook.com Team Why am I getting this?