When writing non-bundle file paths/names to BSO/FLO files, don't use the
delete (^) prefix unless the message has the "Kill Sent" attribute set. This
seems kind of wrong to me. The KFS "Kill File Sent" flag has been defined in
FSC-0053 since 1992, that seems more likely the appropriate flag to determine
if a message attachment should be deleted (or not) after being sent. But
parsing/using the "Flags" control line flags isn't already in SBBSecho, so
I'll just punt for now and do what Mark asked for. <shrug>