Hi Kim,
Thank you for posting in Microsoft Community. I'm here to help.
This usually happens due to sync issues between Outlook and your email server, especially with IMAP or Exchange accounts. It’s common in the New Outlook interface, which has had some bugs with folder management and indexing. Microsoft has acknowledged this as a known issue in certain outlook versions.
Can you let me know if you’re using Outlook on Windows, Mac, or the web? Also, is your account with Microsoft 365, Outlook.com, or another provider? That’ll help figure out whether switching back to Classic Outlook or adjusting sync settings might help.
Feel free to reply for better understanding.
Regards,
Carlo