You can purchase Outlook as a standalone product, if you wish:
https://www.microsoft.com/en-us/microsoft-365/p/outlook/cfq7ttc0hlkq?activetab=pivot:overviewtab
It will be rather expensive, though.
A cheaper alternative is to use the online version of Outlook through your Microsoft account (https://www.outlook.com) or the built-in e-mail app in Windows.