Hi there,
I'm Cherrelyn, and I’m here to help.
If you're seeing the forwarded icon on all incoming messages but nothing is shown in your Sent Items, this is likely a visual bug affecting some Outlook users after a recent update. Your emails aren’t actually being forwarded. Please try restarting Outlook or checking for Office updates. If available, switching back to Outlook (Classic) may also resolve the display issue.
I hope this will help and if you have any question please don't hesitate to reply to this thread.
Warm regards,
Cherrelyn