Conversation View groups emails with the same subject together into a single conversation.
If you prefer every email to appear separately in your inbox, you can turn Conversation View off.
Classic Outlook
Open Outlook and select the View tab.
Untick:
Show as Conversations
Outlook may ask whether you want to apply the change to:
This folder
or:
All mailboxes
Choose the option you prefer.
Emails will now appear individually instead of being grouped into conversations.
New Outlook
Open Outlook and click Settings.
Go to:
Mail > Layout
Under Message organisation, select the option to show emails as individual messages rather than grouped by conversation.
Your inbox will now display each email separately.