Microsoft Outlook will not authenticate and existing Microsoft email account (Outlook for Mac)

Question

I have 3 mac's, one of which is new and in factory reset condition.

I have installed the Office 365 apps on the new mac. One Note syncronises and is working as expected.

However, Outlook fails to add my Email account with an authentication error. I have tried to add the account as a new account, but Microsaoft says it is already regiseted and I should sign in, which then fails with the authentication error.

As an experiment I deleted the account in Outlook on an old mac that has always worked fine. When I tried to re-add the account on this old mac it now also fails to add with a similar authentication error.

I don't know if it is relevant but on the "Manage devices used with your Microsoft account" section of Microsoft Office Support, when I chose to link a mac I see this message:

"Sorry, macOS devices cannot be added at this time."

I bought the new mac specifficaly for the purpose of managing my Outlook email with it.

Does anyone have any advice?

Answer 1

It sounds like you're experiencing authentication issues with Outlook on your Mac devices. Here are some steps you can take to troubleshoot and potentially resolve the issue:

1. Check Keychain Access: Duplicate tokens in the Keychain can cause authentication problems. You can try deleting any cached passwords and modern authentication tokens related to Outlook:
   • Quit Outlook and all other Office applications.
   • Open the Keychain Access app.
   • Search for items related to "Exchange" and delete them.
   • Search for "adal" and delete any items that match.
   • Search for "office" and delete items named Microsoft Office Identities Cache 2 and Microsoft Office Identities Settings 2.
   • Quit Keychain Access and restart Outlook.
2. Update Outlook: Ensure that you have the latest updates installed for Outlook. Install the February 2017 Outlook update (version 15.31.0) or later, as it may resolve authentication issues.
3. Sign Out and Sign In Again: If you are already signed into another account, sign out of all Microsoft 365 apps, then sign in again with the account you want to use.
4. Check for Existing Accounts: If you see a message indicating that the account is already registered, it may be helpful to check the Microsoft 365 Admin Center to ensure that there are no issues with the account itself.
5. Manage Devices: Regarding the message you see about adding macOS devices, this may be a temporary limitation or issue with the Microsoft account management system. You might want to check back later or contact Microsoft support for clarification.

If these steps do not resolve the issue, you may want to consider reaching out to Microsoft support for further assistance.

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References:

• Outlook 2016 for Mac repeatedly prompts for authentication
• Microsoft 365 apps activation error "Another account from your organization is already signed in on this computer"

Answer 2

Hi Chris Rae, thanks for sharing the details. It sounds like you're running into an issue with Outlook authentication across your Macs. Since OneNote is syncing properly, what you can try,

First, Microsoft Account Device Limitations, that “macOS devices cannot be added” message might indicate a backend issue with Microsoft’s device trust system. It could be a temporary service-side bug or a policy restriction tied to your account type (e.g., personal vs. business).

You can try creating a new Outlook profile from scratch, sometimes the default profile gets corrupted and blocks authentication.

Also, try Web-Based Outlook, can you sign in successfully via Outlook on the web? If so, that confirms the account itself is fine and the issue is local to the Outlook app.

I hope this helps you, let me know how it goes.

Chard

Answer 3

Hi Chris Rae, thanks for sharing this workaround, Switching to Legacy Outlook and triggering the IMAP setup via a failed login is a clever trick, for clarity, you might want to highlight that the Advanced option is hidden and requires scrolling, Glad your issue is resolved.

Chard

Answer 4

Hi,

Thanks everyone for your help.

I think I have a work arround to adding an IMAP account from a hoster that is not Microsoft:

Windows:

• Switch to Legacy Outlook if you are using the new interface.
• Use the Add an account option
• Type in the email address.
• When it fails authentication close the error message window.
• You will be taken back to the previous window and see an Advanced option.
• Click advanced and SCOLL DOWN to see the hidden option to add an IMAP account.
• Choose IMAP and proceed as normal.

MAC:

• Switch to Legacy Outlook if you are using the new interface.
• Use the Add an account option to add a false account e.g. XXXX@ YYYY.org.
• It will fail and take you automatically to the configuration page where you can choose the IMAP settings.

Thanks ....Hi,

Thanks everyone for your help.

I think I have a work arround to adding an IMAP account from a hoster that is not Microsoft:

Windows:

• Switch to Legacy Outlook if you are using the new interface.
• Use the Add an account option
• Type in the email address.
• When it fails authentication close the error message window.
• You will be taken back to the previous window and see an Advanced option.
• Click advanced and IMPORTANT - SCOLL DOWN to see the hidden option to add an IMAP account.
• Choose IMAP and proceed as normal.

MAC:

• Switch to Legacy Outlook if you are using the new interface.
• Use the Add an account option to add a false account e.g. XXXX@ YYYY.org.
• It will fail and take you automatically to the configuration page where you can choose the IMAP settings.

Thanks ....