You can change notification sounds for emails and calendar events directly within the new Outlook app for Windows. In classic Outlook, you can choose whether to play a sound when a new email arrives.
If you do not like the existing sound, you can change the new email notification sound on Windows 11/10 using this step-by-step tutorial. You can set existing or custom audio as the new email ...
If you're tired of adjusting Windows volume constantly, EarTrumpet allows you to control individual app volume directly from the taskbar.