--Apple-Mail-16--694122637
Content-Transfer-Encoding: base64
Content-Type: application/pdf;
        x-unix-mode=0644;
        name="bus-schedule.pdf"
Content-Disposition: inline;
        filename=some-file.pdf
(then base64 code here)

--Apple-Mail-18--693549197
Content-Transfer-Encoding: 7bit
Content-Type: application/octet-stream;
        x-mac-type=2A2A2A2A;
        x-unix-mode=0644;
        x-mac-creator=48647261;
        name="somefilename"
Content-Disposition: attachment;
        filename=somefilename
(then the file is here)