The default action for including or not including the name of the message input file as a parameter in the MIME Content-type: header line. This item code specifies that no input file is to be included.
When MTA_CFILENAME has been specified, it will hold for all subsequent input files until an MTA_CFILENAME_NONE action is seen in the same item list.
The item_address and item_length fields are ignored for this item code.