ref: 4bb9e229bcb23826a0fde907667c8fd6565d98d2
dir: /sys/lib/python/email/test/data/msg_37.txt/
Content-Type: multipart/mixed; boundary=ABCDE --ABCDE Content-Type: text/x-one Blah --ABCDE --ABCDE Content-Type: text/x-two Blah --ABCDE --ABCDE --ABCDE --ABCDE Content-Type: text/x-two Blah --ABCDE--