Prior to V8.8
sendmail, this F=L delivery
agent flag caused sendmail to split output lines
in the message body so that they did not exceed 990 characters, and
always caused sendmail to clear the most
significant bit of the characters in those lines.
Beginning with V8.8 sendmail,
F=L emulates this old behavior under certain
conditions. F=L causes
sendmail to assign L= a
default value of 990, if it is missing one (L=), and (if the configuration file level is 1 or
less) to set the F=7 delivery agent flag.