Outlook 365 application error 1001, mail is not syncing

Bradley Wilson 1 Reputation point

Good day

Having an issue with outlook 365 application on Windows 10 PC with error 1001 and the inbox is not syncing. Please could someone let me know why this is, I have tried looking online but can't seem to find much information on this error. What I found is possible issue with not enough memory but when I run task manager there is no issue with performance, memory at about 50%. When I login to Webmail, emails are working fine, so seems to be mailbox/application issue.


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Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Ian Shearman 110 Reputation points

    I found my solution for this issue.

    1. Close all Microsoft applications, office, teams etc.
    2. Go to your AppData folder and navigate to Microsoft (C:\Users*yourusername*\AppData\Local\Microsoft)
    3. Cut/paste the OneAuth and IdentityCache folders out of the Microsoft folder and paste it onto your desktop.
    4. Relaunch Outlook and sign in. It might already be fixed at this point. If not, close out of Outlook, copy the OneAuth and IdentityCache folders back into the Microsoft AppData folder but.. when it asks if you want to overwrite, say NO.
    5. Relaunch Outlook and sign in, should be working now.
    22 people found this answer helpful.

  2. Sysarrow 31 Reputation points

    Hi, I have a same problem and the solution is restore appx profile.

    I atachedd script

    User's image

    4 people found this answer helpful.

  3. Odysseas Tsakiridis 20 Reputation points

    Hi, I have a same problem and this is my solution that works to me:
    Sign out from Office, not only from Outlook.
    Sign out the mail account from Windows (Go to settings window, Click on "Accounts", Click on "Access work or school",This should show a window where you can select your account and click disconnect)
    Change your account password
    Rename your PC Name Restart and check again.

    4 people found this answer helpful.

  4. Digital Tips 10 Reputation points
    2 people found this answer helpful.
    0 comments No comments

  5. Yuki Sun-MSFT 40,331 Reputation points

    Hi @Bradley Wilson ,

    Is this a suddenly occurred issue?
    Does it affect others in the same environment as you?

    In case it's due to any corrupted configurations of the existing Outlook profile, please try creating a new Outlook profile and then add the email account again to see if it can work as expected. For steps of creating a new Outlook profile, you may refer to Overview of Outlook e-mail profiles-Create a new profile. Also remember to configure Outlook to prompt you to choose a profile when started so that you can choose the new profile next time.

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