Unwanted Group in Outlook

It sounds like what you have in Outlook is either a Microsoft 365 Group or a leftover “ghost” folder that isn’t behaving like a normal mailbox folder. The easiest first step is to check Outlook on the web to see if the group shows up there, if it does, you can usually leave or delete it from the web version and it will disappear from desktop as well. If it doesn’t show in the web version, then it’s likely just a cached artifact in your Outlook client. In that case, closing Outlook and rebuilding the local cache (by renaming the OST file so Outlook creates a fresh one) often clears it out. If the group turns out to be a real Microsoft 365 Group and you’re not the owner, your admin may need to remove it for you.

------------------------------------
Don't forget to mark as solution if my answer suits you