Sending, receiving, and organizing email in Outlook.com
Hello Michelle Lodge, thanks for posting this in the community.
This issue can happen if there are hidden or server-side rules. Rules created by another user or via PowerShell may not appear in Outlook or OWA. Another possibility is that archiving behavior is controlled by retention tags or mailbox policies rather than rules.
If you have full access to the shared mailbox, open the mailbox in Outlook Web App or Outlook Desktop, go to Settings, then View all Outlook settings, then Mail, and then Rules. Check if any rules are visible and delete them. If no rules appear, the issue is likely server-side or policy-based, which requires an admin. In that case, I suggest reaching out to your IT admin to review this via Exchange.
Kind regards,
John Oli