QUESTION Where is the setting for Delete Fax TIFF after sending email?

[chris_c_]

[2015-08-26 15:53:22] VERBOSE[29331][C-0000000f] pbx.c: Executing [h@ext-fax:4] System("Motif/+1(the cid of the fax machine sending the fax)-0f57", "/var/lib/asterisk/bin/fax2mail.php --to "(my email address)" --dest "(my 10 digit did)" --callerid '"(10 digit cid of the sending fax machine)" <(10 digit cid of the fax machine)>' --file /var/spool/asterisk/fax/1440618588.184.tif --exten "701 (701)" --delete "true" --attachformat "pdf"") in new stack

What page, in the web user interface, is this setting

--delete "true"

located ?

It's not on the page "Settings / Fax Configuration"..

Is it even in the web UI anywhere ?