Specifies how "From:" fields look.
If `nil', they contain just the return address like:
king@grassland.com
If `parens', they look like:
king@grassland.com (Elvis Parsley)
If `angles', they look like:
Elvis Parsley
Otherwise, most addresses look like `angles', but they look like
`parens' if `angles' would need quoting and `parens' would not.