Outlook / Hotmail : unauthorized_client

It makes over a month I am no more able to connect to my Hotmail/Outlook account from EmClient. I made a change in my Microsoft account when the problem happened to be a two step validation which needed me to wait 30 days to be effective.

Now I still have an error, but if I remember correctly the first one, it has changed. It now asks to register the application and this can only be done by the app developers. I am myself a software engineer and I tried to find a way to add a setting in MailClient.exe.config, but still not find (because I already fixed another problem like that, but with another account).

Full message:
We’re unable to complete your request

unauthorized_client: The client does not exist. If you are the application developer, configure a new application through the application management site at https://apps.dev.microsoft.com/.

If the account is set to IMAP and the version you are running is older than v7.2.34959 then take a look at this Reaction to the Outlook.com authentication problem note, which is in fact prominently displayed on the main forum page. Short answer: update to the latest v7.2.35128 build.