+JH/11 Bug 2494: Unset the default for dmarc_tld_file. Previously a naiive
+ installation would get error messages from DMARC verify, when it hit the
+ nonexistent file indicated by the default. Distros wanting DMARC enabled
+ should both provide the file and set the option.
+ Also enforce no DMARC verification for command-line sourced messages.
+