# File lib/mailfactory.rb, line 413
  def quoted_printable_encode_header(text)
    text.enum_for(:each_byte).map do |ord|
      if ord < 128 and ord != 61 # 61 is ascii '='
        ord.chr
      else
        '=%X' % ord
      end
    end.join('').
        chomp.
        gsub(/=$/,'').
        gsub('?', '=3F').
        gsub('_', '=5F').
        gsub(/ /, '_')
  end