The ExtractFile method extracts the attached file stored
in the specified message part, storing it in a file. If the
optional message Part argument is not specified, the current
message part is used. To determine if the current message part
contains an attachment and to determine its file name, check the
value of the Attachment property. An error will be returned
if the specified message part does not contain a file
attachment.
This method will return value of zero if the action was
successful. Otherwise, a non-zero error code is returned which
indicates the cause of the failure.