Dear PeterToplak
Thank you for your reply.
Your two e-mail addresses may have been hacked, if the hacker hacked your account, he can add an alias to your account and then change the alias he added to the main alias, then your account will become an alias under the hacker's account, if the hacker deletes the alias at this time, your account will cease to exist, so your e-mails will disappear in relation to the hacker's operation, you can no longer send and receive e-mails from your account, and when logging in, it will also show your account! You cannot send or receive emails from your account anymore, and your account does not exist when you log in. You can click the link below, enter the cell phone number or email address you used when you registered your account before, and then check back to see if there is any query result, if it shows an unfamiliar account or no result, it's most likely invaded by a hacker!
Here is a link to a related query:Forgotten your Microsoft account username - Microsoft Support
Regarding account loss due to hacking, you can contact the Microsoft Account team's online chat specialists, you can use the reason that your account has been hacked to discuss recovery with the online specialists, who hold more authoritative and more information and expertise than the Microsoft Account community, to see if they have any other ways to help you.
You can click this link to sign in to another Microsoft account, or create a new Microsoft account, and then follow the step-by-step instructions below to get in touch with them
Contact Us - Microsoft Support


Enter your details of the problem e.g. account recovery.
Then tap Contact Support in the bottom left corner.

Choose from the following categories: Other Products, Manage Account Security.


TIPS: Please contact us during local working hours on weekdays, CHAT does not work 24 hours a day.
All the best to you!
Linda.W-MSFT | Microsoft Community Support Specialist