Hi @VictoriaC ,
Are you using your Hotmail email account with Outlook desktop client? If so, what's the type of your account? POP, IMAP or Exchange?
To further confirm if those "disappeared" email messages are still in your mailbox, it is suggested for you to try Outlook search feature to search those emails within your whole mailbox to see if there is any difference.
If you have enabled Outlook archive feature for these folder, issues like this might also happen. Please check your archive settings and if you have indeed enabled it, you could find your email messages in your local archive datafiles.
If you could not find those emails from your desktop client side, then please try to log in to your web mail to check if you could find those email messages there.
Besides, as I know, you could also find part of deleted emails messages via "Recover items deleted from this folder" on your web mail, remember to check there as well.
Any update, please feel free to post back.
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