Dear Default__628,
Thank you for posting in Microsoft Community.
To better understand your current situation, may I confirm following information?
- May I know if it is Outlook for Windows desktop app that can’t sync your emails? According to your scenario, if you’re using Outlook for Windows app and symptom happens there, please sign in mail web version in advance to make sure emails are received and stored by mail server.
- Please manually check updates for Outlook and Microsoft 365 Apps to make sure it’s in the latest version. May I know the Office suite edition you’re using (Microsoft 365 Apps for Business , for Enterprise or other edition)?
- In Outlook for Windows app, please ensure the status bar shows it connected to remote server for your account. Please click “Send/ Receive all folders” in “Send / Receive” tab, then open “Show Progress” window to check if emails will sync to Outlook and whether there’s any sync error in “Show Progress” window.
- May I know affected account type (IMAP, POP or Exchange). If your account is Exchange account, please try to temporarily close Exchange caches mode for your account, restart Outlook to see if it can make any difference. To close cached Exchange mode: In Outlook -> File -> Account Settings -> Account Settings, select your account and click “Change” and untick “Use Cached Exchange Mode to download email to Outlook data file ”, restart Outlook. Please be kindly noted that turning off cached mode may affect Outlook performance, you can turn it on later after test.



If there’s any update, welcome back and feel free to share with us. We look forward to your reply.
Sincerely,
Etta Ma MSFT | Microsoft Community Moderator