Prior to V8.7
sendmail, only the local
delivery agent could recognize a leading /
character as a directive to append the mail message to a file (see
Section 12.2.2 and Section 13.7.3).
Beginning with V8.7, any delivery agent can be made to accept the
leading / character. If the F=/
delivery agent flag is present, the delivery agent will accept a
leading / character and call the
*file* delivery agent to append the mail message
to a file. If the delivery agent flag is absent, this ability to
append is prohibited. In general, the F=/ delivery
agent flag should be present for the local and
local-clone delivery agents but absent for all others. In
configuration files prior to Version 6 (Section 17.5), this delivery agent flag is automatically
set for the local delivery agent.
This delivery agent flag is legal only for addresses contained in
~/.forward files or
aliases(5) databases. Any /
file address in an SMTP dialog
or on the command line will be rejected.