Microsoft fixes bug causing Classic Outlook sync issues with Gmail

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HomeNewsMicrosoftMicrosoft fixes bug causing Classic Outlook sync issues with Gmail

Microsoft fixes bug causing Classic Outlook sync issues with Gmail

By Sergiu Gatlan

March 24, 2026
11:12 AM
0

Microsoft has fixed a known issue causing Gmail and Yahoo email synchronization problems for classic Outlook users.
As the company explained earlier this month, the bug triggers 0x800CCC0F and 0x80070057 error codes when synchronizing Gmail and Yahoo accounts.
Microsoft said that this type of email account stopped syncing as of February 26, 2026, and that, in both cases, users were no longer prompted to sign in to their accounts when Outlook syncing stopped working.
In an update to the original support document, Microsoft says that although the issue was fixed in the Microsoft 365 service on Friday, some customers may still experience sync issues until their OAuth token expires.
"After you change your password, it usually takes one hour for the OAuth token to expire," the company explained on Monday. "After the token expires you will get a sign in prompt from Outlook. If you do not want to wait on the hour you can do the workarounds below to force the sign in prompt."
Customers who can't get their Outlook to sync can also use a temporary workaround shared by Microsoft before the fix rolled out, which requires them to delete the registry entries for the affected email address under the Identities key at Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities in the Windows Registry Editor.

Deleting Outlook Identities (Microsoft)
Microsoft is also investigating a bug that triggers "Can't connect to the server" errors when creating groups in classic Outlook when Exchange Web Services (EWS) is enabled for the tenant.
Another issue, acknowledged almost two months after the first user reports surfaced online, causes the mouse pointer to disappear for some users in classic Outlook, OneNote, and other Microsoft 365 apps.
Microsoft asked affected customers to submit diagnostic log files to assist the Outlook Support Team with analysis by opening a support case through their Microsoft 365 admin.
In January, it addressed another classic Outlook issue caused by the December 2025 updates that prevented Microsoft 365 customers from opening encrypted emails.
Microsoft is also working to address a known issue that will render the classic Outlook email client unusable for users who enable the Microsoft Teams Meeting Add-in.

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Related Articles:
Microsoft investigates classic Outlook sync and connection issuesMicrosoft fixes Outlook bug blocking access to encrypted emailsMicrosoft: Enabling Teams Meeting add-in breaks Outlook ClassicMicrosoft says bug in classic Outlook hides the mouse pointerMicrosoft Exchange Online service change causes email access issues

Classic Outlook
Email
Gmail
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Outlook
Synchronization
Yahoo

Sergiu Gatlan
Sergiu is a news reporter who has covered the latest cybersecurity and technology developments for over a decade. Email or Twitter DMs for tips.

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Microsoft addressed a series of synchronization issues impacting classic Outlook users primarily due to problems with Gmail and Yahoo email accounts. The core of the issue stemmed from 0x800CCC0F and 0x80070057 error codes occurring when attempting to synchronize these accounts, effectively halting the sync process and preventing users from being prompted to re-authenticate. Microsoft initially identified this bug in February 2026, coinciding with the cessation of syncing for these email services. The company’s initial response involved a temporary workaround—deleting specific registry entries under Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities—to force a re-authentication prompt, although this was a manual process. The resolution was formally released on Friday, March 24, 2026.

However, the issue wasn't isolated to these email providers. Microsoft was simultaneously investigating a “Can’t connect to the server” error encountered while creating groups within classic Outlook when Exchange Web Services (EWS) was engaged. Furthermore, a separate, longer-standing problem, recognized nearly two months prior, manifested as the disappearance of the mouse pointer within classic Outlook, OneNote, and other Microsoft 365 applications. Microsoft requested diagnostics from affected users, urging them to open support cases with the Outlook Support Team and submit diagnostic log files for analysis.

Prior to this recent series of issues, Microsoft had addressed another classic Outlook problem resulting from December 2025 updates—namely, the inability of Microsoft 365 customers to access encrypted emails. Additionally, Microsoft was proactively working to resolve a known issue that threatened to render the classic Outlook email client unusable for users who enabled the Microsoft Teams Meeting Add-in. Microsoft's support team acknowledged the complexity of these disparate problems, utilizing a tiered approach to patching and addressing the vulnerabilities. The company’s ongoing investigative efforts aim to mitigate further disruptions and improve the overall stability of the classic Outlook experience, a client that continues to be a significant portion of many users' Microsoft 365 suites.