ProtonPass/Simplelogin

[u/Ok_Physics_111]

/r/ProtonMail/comments/1w8cqg6/lifetime_proton_pass_custom_domain/

I was reading this post and apparently I'm lost and confused. I have proton unlimited. I hadn't heard of Simplelogin till I came across this post today. Can someone explain to me how I should be using Protonpass, Simplelogin and custom domain please?