SPF test with -all

In this test I've added the SPF for my custom domain as follows:

v=spf1 include:_spf.protonmail.ch mx -all

The key thing that could make mail fail is the (-all)

iphone, ios, home screen, close up, pixels, retina, smartphone, icon, mail, email,
Photo by Brett Jordan / Unsplash

Also inserted an image to make it more realistic.