I can't open my Outlook (classic) application on personal desktop

Adam Bukowski-Kruszyna 20 Reputation points
2025-12-01T14:11:54.1166667+00:00

When I try to open my Outlook (classic) application on my personal desktop (Windows 10 Home, as my computer is older and doesn't support Windows 11), it starts off asking me which account to sign in with, then asks for me to verify with one of three options (I select the authenticator app).

Once I approve on my authenticator app, the desktop then comes up with the following error message:

Correlation Id: f4144ffc-72b4-435b-ac7f-4c9ecefe926d

Timestamp: 2025-12-01T14:00:37.000Z

DPTI: 4788eeeddbbc25e580a5841cbc266da78e2d4a7832560a999122707b6d699af8

Message: The credential is invalid.

Tag: 4vt9f

Code: 0

It says to share this with my administrator (there isn't one, as this is my personal computer).

Please advise how to resolve this issue, so I can log in.

Note: I discovered this issue when I clicked on an "email us" link for an estate agent, and it tries to open the application rather than the web browser version. As such, I cannot see the email address for the estate agent (they do not have it written out on their website, only the clickable button).

Outlook | Windows | Classic Outlook for Windows | For home
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Answer accepted by question author
Anonymous
2025-12-01T19:35:17.1+00:00

Hi Adam,

Thank you for the update.

Here's how to remove the old university account from Windows

Remove Account from Windows Settings

Go to Settings > Accounts > Access work or school.

Find your old university account. Click Disconnect.

(This is usually the main problem.) Clear Web Account Manager Cache

Press Win + R, type: %localappdata%\Microsoft\IdentityCache  Delete everything in that folder. (This clears out saved login info.)*

Remove Old Account from Office Open any Office app (Word, Excel). Go to File > Account.

Under Connected Services, remove the university account.

(This stops Office from trying to use it again.) Reset Outlook Profile

Control Panel > Mail > Show Profiles > Remove the old profile.

Make a new one for your personal account.

 

I hope this helps.

 

Best Regards,

Noel

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  1. Anonymous
    2025-12-01T14:50:27.9566667+00:00

    Hi Adam,

    Thank you for sharing your question. Okay, I get how annoying it is when Outlook (classic) won't open, and you see that the credential is invalid message after going through MFA. Usually, this happens because of some old, saved info, problems with your login stuff, or maybe something's not quite right in your Windows setup.

    Here's what you can try to get it working

    Why This Happens

    Outlook saves your login info and other stuff on your computer. If this gets messed up or old – especially after you change your password or something – Outlook can't check if you're really you, even if the MFA thing works.

    Steps to Fix It

    Get Rid of Old Saved Info, Open Control Panel > User Accounts > Credential Manager.

    Look under Windows Credentials and Generic Credentials, and delete anything that says Outlook, Office, or anything about your email account.

    Restart your computer and try logging in again.

    Remove Work or School Accounts, Go to Settings > Accounts > Access work or school.

    Disconnect any accounts listed there. Then, check Settings > Accounts > Email & accounts and remove any accounts that other apps might be using.

    Restart your computer and then re-add your account in Outlook. [learn.microsoft.com]

     

    I hope this helps

     

    Best Regards,

    Noe

     

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