Hi @nikos chatzinicolaou ,
Welcome to our forum!
According to your description, i understand that you are using a Hotmail.com account and the basic authentication is disabled. I'm afraid that you need to use Modern Authentication to connect your Hotmail.com account. As i know:
Outlook supports Modern Authentication in all current Microsoft 365 subscription SKUs and Outlook 2021 LTSC (any SKU with build 11601.10000 or higher) when connecting directly as Outlook.com. If your Outlook is configured to connect to Outlook.com using POP or IMAP, Modern Authentication is not supported.
Please try to create a new Outlook Desktop profile(Control Panel>Mail>Show Profiles>add) and then add your Outlook.com account using automatic account configuration.
More information: Modern Authentication Methods now needed to continue syncing Outlook Email in non-Microsoft email apps.
Hope to help you!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.