Gemini is offering this as a way to fix the slow calendar sync. Does anyone know if it will work and what will break? See Below:
Since “Repair” only provides a temporary fix, you are likely dealing with the EWS Throttling issue.
In eM Client, the “Repair” button clears the local database cache and forces a fresh download. If the lag returns, it means the real-time connection (syncing new changes) is failing. This usually happens because eM Client is using the legacy Exchange Web Services (EWS) protocol, which Microsoft is actively “de-prioritizing” (throttling) in favor of the newer Microsoft Graph API.
If you want to keep eM Client but fix the calendar, you need to force it out of “Legacy mode” and into “Modern mode.”
1. The “Modern” Fix (The Registry Hack)
eM Client actually has a modern sync engine (OAuth2 / Graph), but for many Exchange/Office 365 accounts, it defaults to the old, laggy EWS. You can force it to use the faster API by editing the Windows Registry:
- Close eM Client completely.
- Open the Registry Editor (Press
Win + R, typeregedit, and hit Enter). - Navigate to:
HKEY_CURRENT_USER\Software\eM Client - Right-click in the right pane and create a new DWORD (32-bit) Value.
- Name it:
AllowExchangeOnlineOAuth - Double-click it and set the value to
1. - Restart eM Client.
- Crucial Step: You must now delete and re-add your account. Use the “Automatic Setup.” If it works, it will pop open a browser window for you to log in (Microsoft’s modern login).
Why this works: This forces eM Client to use the same modern “handshake” that the Outlook mobile app uses. It bypasses the old EWS syncing bottlenecks that cause the “lag” you’re seeing in shared calendars.