Microsoft is working on a known problem with Outlook for customers of Microsoft 365 that causes slow starts and freezes as if Offline Outlook Data Files (OST) are being synchronized immediately after launch.
Redmond’s investigation reveals that neither new OST files nor Application event log entries are being created in response to this behavior.
Numerous clients influenced by this issue have additionally revealed that Standpoint will open speedily, immediately, assuming they hit drop subsequent to opening the application.
Customers who are affected, according to Microsoft, may also notice that the application will not start on systems with airplane mode enabled.
Users will encounter errors such as “Cannot start Microsoft Outlook” in such situations. The Outlook window won’t open. It is impossible to open the set of folders. The attempt to access Microsoft Exchange has been unsuccessful.”
During cache re-priming, which takes place when creating new profiles or deactivating shared calendar improvements, Outlook freezes and starts very slowly.
Cache repriming is one known cause of this symptom. Microsoft states, “This is anticipated if the user has created a new profile or manually switched from REST to MAPI by deactivating Shared Calendar Improvements.”
“However, running such applications can force this toggle unexpectedly due to endemic problems in the reading service enabled feature’s status.”
Workaround available
The Outlook team is looking into and fixing this issue right now because the app was having trouble figuring out what Microsoft called the “default” state of the cache.
This occurs because non-Office MAPI applications such as MFCMAPI and Outlook will arrive at distinct conclusions, resulting in unexpected hangs and sluggish starts.
According to a support article that was published today, affected Outlook users can accomplish this by turning on the “Shared Calendar Improvements” option in the Exchange Account Settings dialog. After selecting the “Advanced” tab and clicking More Settings, the change will take effect after Outlook is restarted.
On affected systems, IT administrators can also use a group policy setting to enable Outlook REST calendar-sharing updates.
Another problem that prevented Outlook for Microsoft 365 customers from accessing their emails and calendars was fixed by Microsoft in April.
In October 2022, Redmond also shared temporary solutions for login issues and a bug in August 2022 that caused Outlook to freeze and crash shortly after launch.
