MS Outlook: can't synchronize email accounts

Question

Starting about a week ago, I have intermittently been having difficulty getting MS Outlook to synchronize with my email server. My ISP tells me that somehow Outlook is creating a cloud service redirect and failing to allow me to access the ISP email server. How can I fix it back to the way it was a week ago?

Answer 1

I thought it would be Spectrum/Charter as well.

Many users have reported this issue lately, but whoever you spoke to apparently doesn't know that this is an issue Spectrum already (finally) acknowledged on their community forum and is working on.

Also this is not an issue unique to Microsoft email client either. I spoke to others who also reported issue on macOS using Apple Mail. See this example: https://learn.microsoft.com/en-us/answers/questions/5982927/outlook-for-mac-has-been-unable-to-sync-with-my-ch

https://community.spectrum.net/discussion/179570/odd-problem-accessing-charter-net-email

Answer 2

If the affected account is Gmail or Yahoo in classic Outlook, this matches a known Outlook for Microsoft 365 issue that started in late February 2026 and can show up as intermittent sync failures, including 0x800CCC0E, 0x800CCC0F, or 0x80070057.

The supported workaround is to force Outlook to prompt for sign-in again by removing the stored OAuth credential:

1. Close Outlook.
2. Open Credential Manager from the Windows Start menu. On Windows 10, this may require opening Control Panel first.
3. Select Windows Credentials.
4. Under Generic credentials, find entries that start with MicrosoftOffice16_Data:OAUTH2.
5. Remove the credential that matches the affected Gmail or Yahoo account.
6. Reopen Outlook and sign in again when prompted.

If the problem started after a password change, Outlook may not prompt immediately because the OAuth token can take about one hour to expire. After it expires, Outlook should prompt for sign-in.

If the account is a POP or IMAP account with an ISP mail server rather than Gmail or Yahoo, the context supports these checks:

1. Verify the account settings in Outlook are correct, especially the user name, password, and server settings.
2. Check whether the network or ISP is blocking the outgoing SMTP server. If so, ask the ISP for an alternative SMTP server and update the outgoing server setting.
3. Check whether a proxy server is required on the network.
4. Confirm the mail server is actually online.

If Outlook shows different mail than Outlook on the web, or mail appears in webmail but not in Outlook, the issue can also be caused by a corrupted .ost file or Outlook synchronization problem.

A quick verification step in Outlook is:

1. Right-click an offline folder.
2. Select Properties.
3. Open the Synchronization tab.
4. Compare Server folder contains and Offline folder contains.

If those counts do not match, Outlook is not syncing correctly.

For a broader Outlook client repair on Windows 11:

1. Open Settings > Apps > Installed Apps.
2. Find Microsoft 365 or Microsoft Office.
3. Select the three dots > Change > Online Repair > Repair.
4. Restart Windows after the repair.

Caution: removing credentials only affects stored sign-in data, but removing accounts or deleting local-only folders can cause data loss if items are stored in folders marked This computer only.

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References:

• Users get errors 0x800CCC0E & 0x800CCC0F synchronizing Gmail and Yahoo accounts in classic Outlook
• I can't send or receive messages with Outlook for Mac
• Issues when you synchronize your Exchange Server mailbox with your .ost file in Outlook
• Synchronization problems occur in Outlook and in Outlook Web App
• How do I fix synchronization error 8004010F-0-0-560 Microsoft 365, Windows 11 - Microsoft Q&A