Fix Outlook 0x800CCC0E Gmail and Yahoo Sync Errors

In early 2026, classic Outlook for Windows stopped syncing some Gmail and Yahoo accounts and logged errors 0x800CCC0E or 0x800CCC0F instead of asking you to sign in. Microsoft traced it to a change on its own servers and corrected that on March 20, 2026, so the underlying bug is gone. If you still see these errors today, it almost always means Outlook is holding a stale sign-in for the account, and clearing it gets the sync working again.

What the errors look like#

The problem shows up as a sync that quietly stops. Outlook keeps running and the account stays in your folder list, but new mail never arrives and nothing sends. Rather than prompting you to sign in again, it records one of these errors, which you can see in the send/receive progress window.

Error you see	When it appears
Task 'Synchronizing subscribed folders for [email protected]' reported error (0x800CCC0E)	Outlook tries to pull new mail for the account
Check for new mail reported error (0x800CCC0E)	A manual or scheduled send/receive runs
Sending reported error (0x800CCC0F) or (0x80070057)	You try to send a message from the account
The account simply stops updating, with no prompt	Sync fails silently in the background

These are the exact strings Microsoft lists for the issue. 0x800CCC0E and 0x800CCC0F are generic connection errors, so seeing them does not by itself prove you hit this specific bug. But paired with a Gmail or Yahoo account that stopped syncing around late February 2026, it is the likely match.

What Microsoft says is going on#

Microsoft documented this as a known issue affecting Gmail and Yahoo accounts in Outlook for Microsoft 365, the desktop app now called classic Outlook for Windows. Accounts began failing to sync on February 26, 2026. The cause was a change in the Microsoft 365 service itself, not something on your PC, which is why it hit accounts that had been working fine and needed nothing from you to break.

Detail	What Microsoft confirmed
Affected app	Outlook for Microsoft 365 (classic Outlook for Windows)
Affected accounts	Gmail and Yahoo accounts connected to classic Outlook
Symptoms	Sync stops; errors 0x800CCC0E, 0x800CCC0F, or 0x80070057; no sign-in prompt
Started	February 26, 2026
Status	Fixed by a Microsoft 365 service change on March 20, 2026
Notice last updated	March 23, 2026

Because the fix was applied on Microsoft’s servers, there is nothing to install to receive it. The service change corrected the root cause on March 20, 2026, and the notice has not reported a return of the problem since.

If you still see the error#

Microsoft calls out one catch. These accounts connect with modern authentication, meaning Outlook holds a token that stands in for your password instead of storing the password itself. If you change your Google or Yahoo password, that old token stops working, and Microsoft notes it can take up to an hour to expire. During that window Outlook may keep failing with the same errors before it finally shows a sign-in prompt. Often the fix is to wait about an hour and sign in when asked.

If the errors persist, Microsoft gives two ways to force Outlook to forget the stale sign-in and re-authenticate. The first is safer, so try it first.

The safer method removes the account’s saved credentials:

1. Close Outlook completely.
2. Open the Start menu, search for Credential Manager, and open it.
3. Choose Windows Credentials.
4. Find the entries that begin with MicrosoftOffice16_Data:OAUTH2 for the affected account. There are usually a few per account.
5. Expand each one and choose Remove.
6. Reopen Outlook. It should prompt you to sign in to the Gmail or Yahoo account again.

Signing back in is a normal Google or Yahoo login, and it is a sensible moment to confirm the account’s own security is in order — our walkthrough on how to set up two-factor authentication covers that. One caution: a genuine re-authentication prompt looks a lot like the fake ones scammers send, so make sure the sign-in page really belongs to Google or Yahoo before you type your password. Our guide on how to spot a phishing email explains what to check.

The second option edits the Windows registry, which carries real risk if you change the wrong key. Back up the registry first — Microsoft links its own backup-and-restore guide from the notice — and while you are at it, make sure your important mail and files are backed up, which our guide on how to back up your files properly walks through.

1. Close Outlook.
2. Open the Start menu, type regedit, and open Registry Editor.
3. Go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities.
4. Find the subkey named for the affected Gmail or Yahoo address and delete it.
5. Restart Outlook and sign in when prompted.

Both methods do the same thing in the end: they clear the outdated sign-in so Outlook asks Google or Yahoo for a fresh one. Pick based on how far you want to go.

Approach	Difficulty	When to use
Wait about an hour, then sign in	Easiest	You just changed the account password
Remove the account’s saved credentials	Moderate	Errors continue after the service fix
Delete the account’s identity key in the registry	Advanced	Removing the credentials did not clear it

Keeping Gmail and Yahoo steady in Outlook#

The core bug is already fixed on Microsoft’s side, so there is nothing to roll back and no update to chase. Keep classic Outlook current through File > Office Account > Update Options > Update Now so you have the latest handling of these connections, and remember that any time you change your Google or Yahoo password you should expect Outlook to ask you to sign in again. If a fresh sign-in still does not restore the sync, the generic nature of 0x800CCC0E means the trouble is likely elsewhere — a connection problem, or account settings on the Gmail or Yahoo side — rather than this particular known issue.

Sources: Users get errors 0x800CCC0E & 0x800CCC0F synchronizing Gmail and Yahoo accounts in classic Outlook, Microsoft Support. Corroborating coverage: Microsoft finally fixes Classic Outlook bug breaking Gmail sync, Neowin.