@vitor According to Step 3, Alfred will find everything that is checked in the Spotlight preferences. However, Alfred doesn't actually display those files unless you add the folder with those files to the Search Scopes. Most people probably don't understand that, or even know that emails are stored in ~/Library/Mail, and that fonts are stored in /Library/Fonts and ~/Library/Fonts.
My suggestion would be to add those 3 paths to the default Search Scopes, and then add checkboxes for "Emails" and "Fonts" under Essentials or Extras to hide those results.