def standard?
      self.syntax = :invalid
      self.valid_size? or return false
      self.valid_encoding? or return false
      if self.local =~ STANDARD_LOCAL_REGEX
        self.syntax = :standard
        true
      else
        false
      end
    end
def standard?
      self.syntax = :invalid
      self.valid_size? or return false
      self.valid_encoding? or return false
      if self.local =~ STANDARD_LOCAL_REGEX
        self.syntax = :standard
        true
      else
        false
      end
    end
True if the part matches the RFC standard format