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.