I wish it was possible to let users manually white list domains. Emails could contain some form of standard header to ask users if they want to white list/add

I wish it was possible to let users manually white list domains. Emails could contain some form of standard header to ask users if they want to white list/add an address to their contact list, and other emails would be down as default. I know email is a good protocol, but reading email headers made my eyes bleed.