New Outlook: "Changing the ImapRemoteServerInfo is not allowed" after host migration

Hi everyone!

I've migrated my domain/mailbox from one IMAP host to another in May. It cannot be added to New Outlook for Windows — fails instantly with INVALID_CREDENTIALS INTERACTION_REQUIRED, even when I deliberately enter a wrong password (so it's failing before authentication is even attempted).

Using DevTools (olk.exe -devtools), the Network tab shows the real rejection from Microsoft's backend:

Changing the ImapRemoteServerInfo is not allowed. Attempted to change it from imap.olddomain.sk to imap.newdomain.sk

So New Outlook has a cloud-mailbox / connected-account shadow record for this address, pinned to the old host from a previous add attempt, and the backend refuses to update it. What I've confirmed:

• Webmail and a second mailbox on the same domain/host both work fine → not credentials, not the host.
• The account does not appear in Settings → Accounts (so I can't use "Remove from all devices" which worked on my first account).
• It's on no other device or client.
• App reset didn't help (record is server-side, not local).
• It's been ~7 weeks, so any 30-day inactivity purge hasn't cleared it

How do I get this stuck cloud-mailbox / connected-account record purged when it isn't attached to any removable account? Is there a way to force it, or does this need Microsoft backend action?