Sudden sync issue with IMAP email and Outlook

Question

I have the correct username and password for my IMAP email, but it suddenly will no longer sync with my Outlook

Answer 1

Hi Kevin Flannery,

Welcome to Microsoft Q&A.

Based on the symptoms you described, Gmail IMAP suddenly failing to sync in classic Outlook with the error “Synchronizing subscribed folders” (0x800CCC0E) this matches a known issue that Microsoft has documented with Gmail OAuth permissions in classic Outlook.

This can occur when a Gmail account was already added to Outlook, but during the Google browser sign‑in flow, the required permission for Microsoft apps to access Gmail was not fully granted or the OAuth token later became invalid. When that happens, Outlook can no longer synchronize subscribed folders and send/receive may fail.

Microsoft has officially confirmed this behavior and published a fix.

Status

Fixed starting with Current Channel Version 2412 (Build 18324.20168).

What to do next

If your Outlook is fully updated to the fixed build:

• When the error appears, select the Retry link in Outlook.
• This will prompt the browser sign‑in again.
• Make sure the permission “Read, compose, send, and permanently delete all your email from Gmail” is checked during sign‑in.

If the Retry option doesn’t resolve it, use the manual workaround below:

Manual Workaround

1. Remove Microsoft access from your Google account

• Close Outlook.
• Sign in to your Google account.
• Go to Security > Your connections to third‑party apps & services.
• Select Microsoft apps & services > Remove all access and confirm.

2. Delete Google IMAP OAuth credentials from Windows

• Open Credential Manager > Windows Credentials.
• Under Generic Credentials, remove entries starting with: MicrosoftOffice16_Data:OAUTH2 (specifically those tied to tp_google_imap_Oauth2).
• Make sure both credentials related to the Gmail account are removed.

3. Sign in again from Outlook

• Reopen Outlook and sign in via the browser when prompted.
• Ensure the Gmail permission mentioned above is checked.
• If you removed the account earlier, add it back via File > Add Account and complete the browser sign‑in.

Microsoft has published the full guidance here for reference: Unable to add a Gmail account to classic Outlook

Important note

This applies to classic Outlook for Windows using IMAP. The new Outlook app uses a different sync model and isn’t affected in the same way.

If you’re still seeing issues after completing the steps above, feel free to share your Outlook build number and whether the account was added before or after the update, and we can take a closer look.

Hope this helps get things syncing normally again.

Please let me know if this proves useful to you, or if you would like further assistance.

I'm looking forward to your reply.

---

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Use the following checks and fixes in order, focusing on IMAP-specific issues in classic Outlook:

1. Confirm the account type in Outlook

• In classic Outlook, go to File > Account Settings > Account Settings...
• On the Email tab, confirm the account is set up as IMAP (not POP, Exchange, or Microsoft 365) according to what the provider requires.
• If this is an Outlook.com/Hotmail/Live address, make sure it is added using the correct account type (for example, Outlook.com rather than IMAP/POP). Using the wrong type can prevent proper sync of messages and folders.

2. Recreate the IMAP account in Outlook If sync suddenly stopped and credentials are correct, recreating the profile often fixes corruption.
3. Close Outlook.
4. Open Control Panel > Mail.
5. Select Email Accounts....
6. On the Email tab, select the IMAP account and choose Remove.
7. Then select New.
8. Enter name, email address, and password in the Password and Retype Password boxes, then select Next.
9. Follow the prompts until setup completes, then select Finish and restart Outlook.
10. Check for IMAP connection/security issues

• If the IMAP server recently changed security requirements (for example, TLS/SSL versions), Outlook may fail to sync.
• If there are errors like the server unexpectedly terminating the connection, and TLS 1.3 is enabled in the Windows Schannel configuration, follow the documented workaround:
  1. Open Registry Editor and navigate to the Protocols key under Schannel.
  2. If TLS 1.3 appears under Protocols, export that key as a backup, then delete the TLS 1.3 key and its subkeys.
  3. Restart Outlook; if sync still fails, restart Windows. This addresses cases where IMAP/POP connections are interrupted due to TLS 1.3 issues.

4. Check for password/authentication problems specific to IMAP

• If Outlook never prompts for a password when using IMAP, ensure Require logon using Secure Password Authentication (SPA) is unchecked in the account’s IMAP settings.
• If authentication fails and the IMAP password contains Unicode characters (such as ä, ö, ü), change the email account password so it uses only non-Unicode characters, then update it in Outlook. Outlook 2016 and later can fail IMAP authentication with such characters.

5. Verify server and port settings with the provider

• Confirm with the email provider that the IMAP server name, port, and encryption type (SSL/TLS) have not changed.
• In Outlook, open the account’s More Settings and verify:
  • Incoming server (IMAP) address and port
  • Outgoing server (SMTP) address and port
  • SSL/TLS options match the provider’s requirements

If, after these steps, the IMAP account still will not sync, contact the email provider to confirm there are no server-side blocks or changes (for example, IMAP disabled, security policy changes, or app-password requirements).

---

References:

• Troubleshoot Outlook email setup
• Authentication fails when you use an IMAP server in Outlook 2016
• Outlook IMAP or POP server unexpectedly terminated the connection, and the server was interrupted