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AndreaR's avatar
AndreaR
Copper Contributor
Mar 18, 2025

Non-Office 365 accounts repeatedly request sign-in each time Outlook (new) is opened or restarted

My Setup :

  • Operating System: Windows 11 (fully updated, including latest Dell laptop BIOS/firmware)
  • Office Version: Microsoft 365 Apps (licensed under Office 365 Standard for one of the email accounts)
  • Outlook Version Used: Primarily the New Outlook for Windows
  • Email Accounts Involved:
    • One Office 365 Exchange account: email address removed for privacy reasons (credentials persist without issues)
    • Multiple Gmail/IMAP/SMTP accounts (e.g., email address removed for privacy reasons, email address removed for privacy reasons, email address removed for privacy reasons, email address removed for privacy reasons) (all require reauth every time Outlook is opened)

Symptoms

  • Non-Office 365 accounts repeatedly request sign-in each time Outlook is opened or restarted.
  • No error messages—just continuous web auth prompts for Gmail, SMTP, and IMAP accounts.
  • The single licensed Office 365 account retains its credentials without issues.

Troubleshooting Steps Already Tried

  1. Uninstalled/Reinstalled Office 365
    • Completely removed Microsoft 365 (via Apps & Features or Control Panel).
    • Reinstalled Office 365—accounts still persisted upon first launch of Outlook, leading to repeated sign-in prompts again.
  2. Cleared Windows Credential Manager
    • Removed all stored credentials related to Outlook, MicrosoftOffice16_Data:OAUTH2, Gmail/IMAP references, etc.
    • Verified credentials were gone before relaunching Outlook.
  3. Removed Registry Keys & Data
    • Under HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity, deleted leftover Identities referencing old accounts.
    • Under HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Settings, removed the Accounts key containing JSON references to old addresses.
    • Removed/cleaned up values in the Data subkey referencing _AccountSignaturesMigrated, _UserOptionsMigrationState, etc.
  4. Deleted Local AppData & Roaming Outlook Folders
    • %LOCALAPPDATA%\\Microsoft\\Outlook
    • %APPDATA%\\Microsoft\\Outlook
    • Checked/removed possible OST/PST data in %USERPROFILE%\\Documents\\Outlook Files
  5. Removed Email & Accounts in Windows Settings
    • Under Windows 11 Settings → Accounts → Email & accounts, confirmed the problematic addresses were removed.
  6. Checked for Security Software Conflicts
    • No third-party antivirus, firewall, or VPN is interfering.
  7. Tried “New Outlook” Command-Line Wipe
    • Attempted outlook.exe --clearLocalState (or olk.exe --clearLocalState) to remove local cache.
    • Re-launched Outlook, re-added accounts—still facing reauth loops.
  8. Ensured Windows & Dell Firmware/Bios Up to Date
    • Double-checked the system is fully updated (Windows Updates, Dell updates).

Result

  • Issue Not Resolved: Gmail/IMAP accounts continue prompting for sign-in each time Outlook starts.
  • Only the Office 365 Exchange account retains its credentials as expected.
  • After exhaustive attempts, reverted to Classic Outlook because it does not prompt for repeated sign-ins.

Please let me know if this is a known bug that Microsoft is actively addressing. Are there any other steps I can take beyond local registry/credential cleanup to permanently resolve the repeated OAuth prompts?

outlook for windows
  • LucasTurner's avatar
    LucasTurner
    Iron Contributor
    Mar 29, 2025

    1. Quick fixes
    Delete and re-add the account
    File → Account Settings → select the problem account → click “Delete”
    Re-add the account after restarting Outlook
    2. Clear Credentials Cache
    Open Windows Credential Manager (control.exe /name Microsoft.CredentialManager)
    Delete all credentials related to Outlook.
    3. Common causes and targeted solutions
    Scenario A: Outdated authentication methods
    Ensure that the account uses modern authentication (OAuth2):
    File → Account Settings → select the account → click “Change”
    Check “Use modern authentication” (if option is available)
     Scenario B: Third-party mail service restrictions
    Check if the mail provider supports OAuth2:
    Gmail/Yahoo etc. need to enable “Allow insecure applications” on the web side
    Enterprise mailboxes need to contact IT administrator to open API privileges
    4. Registry Repair (Windows)
    Force modern authentication to be enabled:
    Press Win+R and type regedit
    Navigate to:
    HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity  
    New DWORD value:
    Name: EnableADAL
    Value: 1
    5. Special configuration for enterprise environment
    Group Policy Adjustment:
    Administrator Run gpedit.msc
    Navigate to:
    Computer Configuration → Administrative Templates → Microsoft Outlook 2016 → Account Settings → Accounts
    Enable:
    “Force use of modern authentication”
    “Disable ADAL” is set to Disabled
    6. Alternatives
     Use application-specific passwords (e.g. for Google accounts):
    Generate a 16-digit dedicated password in the backend of your email provider
    Use this password instead of the master password for Outlook logins

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