Default mail app status
This build does not register as the macOS default mail app, so
mailto: links and .eml files open in whatever app the system
already uses.
What to do instead
Section titled “What to do instead”- Compose in Primail with C or File → New Message (⌘N).
- Copy an address from another app and paste it into To.
- Keep using your current default mail app for web
mailto:links.
Support and feedback buttons inside Settings may open a
mailto: URL in that same default app.
Opening a public Primail URL is a separate limit. See Deep-link availability.