Miscellaneous topics that do not fit into specific categories.
For Gmail not syncing in classic Outlook for Microsoft 365, the most relevant fixes are:
- Check whether this is the known classic Outlook Gmail sync issue.
- A Microsoft 365 service-side fix was released on March 20, 2026 for Gmail accounts that stopped syncing and show errors such as
0x800CCC0Eor0x800CCC0F. - If Outlook is not prompting for sign-in after a password change, it can take up to one hour for the OAuth token to expire before Outlook prompts again.
- A Microsoft 365 service-side fix was released on March 20, 2026 for Gmail accounts that stopped syncing and show errors such as
- Force Outlook to prompt for Gmail sign-in again.
- Close Outlook.
- Open Credential Manager from the Windows Start menu.
- Go to Manage your credentials > Windows Credentials.
- Under Generic credentials, find entries starting with
MicrosoftOffice16_Data:OAUTH2. - Expand them and identify the ones that include
tp_google_imap_Oauth2. - Remove each matching Gmail credential.
- Restart Outlook and sign in to the Gmail account.
- Restart Outlook again if mail does not begin syncing immediately.
- Verify Gmail IMAP is enabled.
- In Gmail, go to Settings > Forwarding and POP/IMAP.
- Under IMAP Access, select Enable IMAP.
- Save changes.
- Verify Gmail folders are available to Outlook.
- In Gmail, go to Settings > Labels.
- Make sure Show in IMAP is selected for Inbox, Sent Mail, Trash, and All Mail.
- If the problem started while adding the Gmail account to Outlook, check the Google consent step.
- When Google shows Select what Microsoft apps & services can access, the permission Read, compose, send, and permanently delete all your email from Gmail must be checked.
- In Current Channel Version 2412 Build 18324.20168 and later, the error window includes a Retry link to repeat the browser sign-in if that box was missed.
- If automatic setup keeps failing, try manual setup in classic Outlook.
- Go to File > Add Account.
- Enter the Gmail address.
- Select Advanced options > Let me set up my account manually.
- Choose POP or IMAP.
- If needed, use Gmail IMAP settings:
- Incoming server:
imap.gmail.com, SSL, port993 - Outgoing server:
smtp.gmail.com, SSL port465or TLS/STARTTLS port587
- Incoming server:
If the issue is specifically that Outlook sends but does not receive, and the account is Gmail, step 2 is the strongest first action because it forces Outlook to refresh the Gmail OAuth credentials.
Warning: deleting the wrong registry key or identity entry can affect account sign-in state. If using the registry-based workaround, only remove the identity that matches the affected Gmail account.
References: