ログの出力例)
Mon dd hh:mm:ss HEADER Body (RFCtoX400) :
Content-Type: application/yyyyyyy;
name="=?iso-2022-jpXXXXXXXXXXXXXXXXXX?=
=?iso-2022-jpXXXXXXXXXXXXXXXXXXXXXXXXX?=
Content-Disposition: attachment;
filename="=?iso-2022-jpXXXXXXXXXXXXXXXXXX?=
=?iso-2022-jpXXXXXXXXXXXXXXXXXXXXXXXXX