Hi there TOosterbaan. I am Lumie and I would love to assist you today.
I am so sorry you are having issues with your account passwords.
What is likely going on is that the account is being attacked by a botnet. (Which is called a brute force) This means Microsoft will try to protect your account by forcing you to change your password.
Please keep in mind, these passwords should be new, not from a dictionary of commonly used password. This is to protect your online experience.
You can see if they are trying to break into your Hotmail by logging into this part of your account: [account.live.com/Activity]
In order to fix this, we can change your alias, the leaked information is no longer relevant and you will no longer receive spam log-ins.
"Go to Add an alias.
Sign in to your Microsoft account, if prompted. [https://account.live.com/AddAssocId]
Under Add an alias, do one of the following:
Create a new Outlook.com email address and add it as an alias.
Add an existing email address as an alias.
Select Add alias."
Now you can go to this site: [account.live.com/SignInPreferences] and turn off your sign in options for the past alias.
Your email address will operate completely as normal, but now you must sign in with another email address.
These steps and more information can be found here: [https://support.microsoft.com/office/459b1989-356d-40fa-a689-8f285b13f1f2]
I hope this helps!
Let me know if I can be of any further assistance. -Lumie =)