IMAP connection error INVALIDCREDENTIALS

I am trying to add my external IMAP mailbox from my hosting provider (Easyhost.be) to the new Outlook app / Outlook.com.

However, when I try to add this mailbox to my domain 'vinedo.be', I immediately receive the error message: INVALIDCREDENTIALS INTERACTIONREQUIRED.

In the classic Outlook desktop app, the account works immediately via IMAP with exactly the same password. Everything also works perfectly with the Outlook app on an Android smartphone.

There appears to be an incorrect tenant attribution or cache in the background of the Microsoft Cloud that is internally blocking authentication for the domain vinedo.be.

Could you clear the cache/tenant attribution for the domain vinedo.be so that the IMAP connection is routed externally again?

The mailbox email address removed for privacy reasons was hosted by Gandi.net until recently. This is presumably causing the problem.