Using classic Outlook for Windows in educational settings
Hello joyfulSandfish,
Greeting. Thank you for posting to Microsoft Community.
Based on your description, I understand your query is about “Outlook 365 - "You replied to this message" / fowarded / etc. not showing up on all emails”. I did thorough research and testing from my end.
May I know if you're referring to the similar prompt line shown in the image below?
May I know the affected user's account type and on what device he is using?
It seems that this feature appears to be undergoing an update, as shown in the image below. It is no longer visible for New Outlook for Mac and some Windows version.
Please check if the affected user's email display the status of the message with a small icon. You may see the Reply or Forwarded icon instead. If replied, it will appear as a small arrow to the left, and the forward is an arrow to the right. Example attached.
If so, please let us know, and noticed that you mentioned that "not showing up on all emails" "one of our computers it doesn't show up" "(we have a mixed OS network) so the mail account is synced via imap", seems for some it works and for some not. so please send us affected user's details of Outlook version and screenshots for further analysis, once get more details, we will perform more test from our side.
What version of Outlook do I have? - Microsoft Support
We value your organization information security, please share us information and screenshot via private messages.
For private message: Please click account you logged in on the up-right corner - My profile - View private messages to get it. (I already send one message to you)
Your understanding and cooperation are greatly appreciated.
Have a good day.
Best regards,
Winter| Microsoft Community Moderator