The default reply method in Office 365 is reply all (which is different to the Outlook desktop client installed on University computers).
See Also
Send automatic out of office replies from Outlook for WindowsHow do I turn off or disable the default "Request Responses" from the Response Options in Outlook 365? - Microsoft Q&AHow do I turn off suggested replies?Use suggested replies in OutlookThis guide will show you how change the setting from 'reply all' to 'reply' in Office 365.
- Click on the settings cog in the top right hand corner of the Office 365 Web App
- Select Mailtowards the bottom under Your app settings
- Under the Mail section on the left hand side, select Reply Settings
- Change 'my default response' to Reply
- Review the settings and click Save
