The following articles were included in our Exchange Messaging Outlook (EMO) newsletter published on March 12, 2026.
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Today's Highlights »
- Sync Issues and Errors with Gmail and Yahoo accounts
- Can you restore a copy of an IMAP or Exchange Data File?
- Search Folders in New Outlook
Sync Issues and Errors with Gmail and Yahoo accounts
Microsoft is investigating an issue where users are receiving send and receive error messages in classic Outlook, usually after changing their Gmail or Yahoo passwords.
Typically, they first receive error code 0x800CCCOE, which indicates an authentication error:
Task 'Synchronizing subscribed folders for 'email address’ reported error (0x800CCCOE) : ‘Outlook cannot synchronize subscribed folders for 'email address'. Error: Cannot connect to the server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).
Then error code 0x80070057:
Task 'email address' - Sending’ reported error (0x80070057) : ‘Sorry, something went wrong. You may want to try again.’
The fix is simple: remove the account's credentials from Windows Credential Manager. If that doesn't fix it, remove the account from Outlook and add it back.
1. Close Outlook.
2. Start typing Credential Manager on the start menu. Open it when it comes up (usually after typing 'cred').
3. Switch to the Windows Credentials tab.
4. Scroll down, looking for "MicrosoftOffice16_Data:OAUTH2" in the list.
5. open credential manager and find the MicrosoftOffice data entries
6. Expand each entry. Gmail accounts are shown as "MicrosoftOffice16_Data:OAUTH2:[code]_tp_g", while Yahoo is "MicrosoftOffice16_Data:OAUTH2:[code]". If you hover over the code, you'll see google or yahoo in the full data name.
7. Click Remove to remove the entry from credential manager
8. Click Remove to delete the entry.
9. Repeat for each additional entry.
10. Restart Outlook.
You'll need to enter your password and authenticate the account.
If removing the credentials does not fix the sync issues, you can delete a key in the registry.
1. Close Outlook.
2. Press the Windows key and start typing Registry Editor on the start menu. Open it when it comes up.
3. Paste the path below in the Registry Editor’s Address Bar and press Enter.
Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities
4. Select each sub key and look for the affected address on the right. When you find the address that is not syncing, delete the key (on the left).
Another option is to remove the account from Outlook, then remove the credentials and add the account back.
Note: If you are using "Calendar (This computer only)" and "Contacts (This computer only)" folders in the account's data file, export those two folders to CSV or an Outlook data file before removing the account, otherwise your events and contacts will be deleted forever when you remove the account.
After exporting the calendar and contacts, Remove the account from Outlook. Go to File > Account Settings > Account Settings. Select the account and click Remove. Repeat the steps above.
Screenshot are available in this article: Sync Issues and Errors with Gmail and Yahoo accounts
Can you restore a copy of an IMAP or Exchange Data File?
A user asked if he could move a copy of his IMAP OST to a new computer and use it, rather than downloading everything again.
No, sorry, this is not possible as the OST files for IMAP and Exchange accounts can only be used by the Outlook profile that created them. Even if you are using the same profile that created the OST, you cannot restore a backup copy. IMAP accounts will resync it and Exchange accounts will complaint that the data file is outdated and won’t sync.
OST files are not intended to be backed up as they are synced copies of everything that is on the mail server. The exception is an IMAP data file’s “Calendar (This computer only)" and “Contacts (This computer only)" folders as the contents of those folders are only in that data file. Exporting the contents of those folders to a PST or CSV every now and again is better than backing up the OST.
There are 3rd party utilities that can open an OST for viewing or export (exporting requires a paid license, viewing is free.) Recommended OST to PST utilities are here: Convert an Exchange or IMAP .OST to a .PST
Search Folders in New Outlook
We’re finally getting some improvements in the Search Folder feature in new Outlook. While there is not an option for completely customized search folders like we have in classic Outlook, all the pre-defined search folder options that are in classic Outlook are now available in new Outlook. In addition, you can use Search Folders to search specific folder, not the entire mailbox.
Search folders can be set up in File tab > Settings > Mail > Search Folders.
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My Templates are missing from Outlook
Users get errors 0x800CCC0E & 0x800CCC0F synchronizing Gmail and Yahoo accounts in classic Outlook
Users may get the error "Can't connect to the server" when creating groups in classic Outlook
Users might get the error "This is not a valid style name" in classic Outlook
Other Resources
Sync Issues and Errors with Gmail and Yahoo accounts
Users are reporting send and receive errors with Gmail and Yahoo accounts in classic Outlook. Typically, they first receive error code 0x800CCCOE, which indicates an authentication error, then error code 0x80070057.
Error Opening iCloud Appointments in Classic Outlook
How to fix the iCloud error message 'To help prevent malicious code from running, one or more objects in this form were not loaded.' when trying to open iCloud appointments synced to classic Outlook.