Using classic Outlook for Windows in business environments
Hello mimizebrak
Hi, I'm Karl and will be happy to help you today.
Can assure you that is nothing more then a phishing scam intended only to get the log in credentials to your account. Definitely do NOT sign in to your account on whatever page that link sends you to
#1 - Microsoft would never send out a message like that - wouldn't happen. If there was something that you needed to do, you would see it when you log into your account normally
#2 - There is no "classic version that is going to be replaced by 12/23". While there is still a link to access the old Outlook.com UI, when you log into your account normally, that is the current UI
#3 - Anytime you get a suspicious message with a link in it (not matter who it claims it's coming from), you should always check the underlying URL that the link points to by either hovering your mouse over the link or right-clicking on the link --> select <Copy> --> paste it into any text editor (i.e. Notepad)
#4 Keep in mind that it is very easy for any spammer to make it appear that the message comes from wherever they want by "spoofing" the <From> address so you can never just go by what you see.