outlook.com folders on macbook pro new outlook for mac - not syncing

The behavior matches a sync problem between local Outlook for Mac data and the Outlook.com mailbox, especially because:

• some moved messages appear in Outlook.com on the web,
• one folder stays on Loading... This may take a few moments,
• one folder does not appear in Outlook.com on the web,
• mail send/receive still works for new mail.

Use this recovery path:

1. Check Outlook.com in a browser first.
   • Verify which folders and messages exist there.
   • If a folder or message appears in the browser, it exists on the server.
   • If it exists only on the Mac, it has likely not finished syncing to the server.
2. Check whether the missing content is still local-only.
   • In Outlook for Mac, On My Computer folders are stored only on the computer and are not synchronized with a mail server.
   • Moving mail from On My Computer to an Outlook.com folder should make it server-based, but the current symptoms indicate some items may still be stuck locally or in a broken sync state.
3. If the affected folders are visible in webmail but not correct in Outlook for Mac, clear the cache for the affected folder.
   • In Outlook for Mac, make sure it is connected to the internet.
   • Ctrl-click or right-click the affected folder.
   • Select Properties.
   • On the General tab, select Empty Cache.
   • Let Outlook re-download the folder contents from the server.
   • Risk: emptying the cache can delete information that has not synchronized with the server, so do this only after confirming the folder or items exist in webmail.
4. If the folder is missing only in Outlook for Mac, use the Move tool to locate it.
   • Select any email.
   • Select Move > Copy to Folder...
   • Search for the missing folder name.
   • If it appears, the result can show where the folder is currently nested.
5. If the account was also opened in Legacy Outlook, check whether local folders are hidden there.
   • In Legacy Outlook for Mac: Outlook > Preferences > General.
   • Under Sidebar, clear Hide On My Computer folders.
   • This helps confirm whether the original local-only folders still exist on the Mac.
6. If messages are missing after switching between New Outlook and webmail, remove and re-add the account in Outlook for Mac.
   • Go to Outlook > Settings > Accounts.
   • Remove the Outlook.com account.
   • Add it again and allow it to resync.
   • This is a standard recovery step for Outlook for Mac sync issues.
7. If the missing folder exists in Outlook.com on the web but not on the Mac after re-adding the account, leave Outlook open until the folder list fully rebuilds.
   • A reported case showed Outlook for Mac appeared stuck because a large folder was still rebuilding after a network interruption.
8. If the folder is missing in Outlook.com on the web as well, search for messages from that folder in Outlook.com.
   • For Outlook.com folder issues, items in missing folders may still be discoverable by search.

The key distinction is:

• Visible in Outlook.com on the web = server copy exists and Outlook for Mac can usually be repaired by cache refresh or re-adding the account.
• Visible only on the Mac = the content may still be local-only or never fully synced from the Mac to Outlook.com.

• About On My Computer folders in Outlook for Mac
• How to retrieve a lost email folder on my Macbooki - Microsoft Q&A
• Lost email subfolders under a main folder which was renamed - Microsoft Q&A
• Losing emails when switch to New Outlook - Microsoft Q&A
• outlook for Mac not syncing - Microsoft Q&A