Mails disapear from day to day

On a Windows 11 PC, 24G RAM
emails dated between yesterday and February 11, 2026, disappear.
After a repair, they reappear.
After a restart the following day, they are gone again.

Synchronization Options
Synchronize messages within: Anytime
Automatically download messages for offline use and search
Complete messages (excluding attachments)
[-] Enable smart optimization for faster downloads
[-] Enable raw download (entire message at once)
Special Folders
Automatically detect folder names

thanks in advance