Hi @roughlee
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Based on your description, we understand that a specific IMAP account seems unable to access Outlook.
To help address the issue more effectively, could you please provide additional details for the following question:
As you mentioned, this issue affects some PCs while others are working fine. Could you check and compare the Outlook build versions to see if the issue is related to a specific version? You can find the version in Outlook > File > Office Account > About Outlook.
Also, did this behavior start after any recent changes, or is this the first time this account has been connected to Outlook?
Just to clarify, could you confirm whether the business account receiving this response code is managed through Exchange Online, on-premises Exchange, or another mail hosting service? If it’s managed through exchange online, you might consider asking your administrator to reset the affected account. This will allow the user to re-register MFA and potentially resolve the issue. You can refer via: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID |…
I will be waiting for your response. If you need further assistance, please let us know.
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