You can make Shortwave your default email app by following the instructions below for your device or browser.
Once enabled, Shortwave will automatically open any time you follow an email link.
From the Mail menu, choose Preferences (or Settings)
Click the General button
Choose Shortwave from the “Default email reader” dropdown menu
Windows
Open Settings > Apps > Default Apps
In the right panel under the Email section, click the existing default mail app
Select Shortwave from the dropdown list
Web app
Along with setting your web app preferences, you can also set your computer to open your default browser to email links. You can do this by following the relevant Desktop app instructions above and choosing your preferred browser as your default mail handler (instead of the Shortwave desktop app).
Doing this ensures that other non-browser apps also send you to Shortwave in your preferred browser.