sendmail, 4th Edition

F=

Delivery agent flags All versions

The F= delivery agent equate is probably more fraught with peril than the others. The delivery agent flags specified with F= tell sendmail how the delivery agent will behave and what its needs will be. These delivery agent flags are used in one or more of three ways.

First, if a header definition relies conditionally on a delivery agent flag:

H?P?Return-Path: <$g >
  ↑
  apply if P delivery agent flag is specified in F= delivery agent equate

and if that delivery agent flag is listed as a part of the F= delivery agent equate:

Mlocal, P=/bin/mail, F=rlsDFMmnP, S=10, R=20, A=mail -d $u
                               ↑
                               apply in header

that header is included in all mail messages that are sent via this delivery agent.

Second, if a delivery agent needs a special command-line argument that sendmail can produce for it but requires that argument only under special circumstances, selected F= delivery agent flags can produce that result. For example, the F=f delivery agent flag specifies that the delivery agent needs a -f command-line switch when it is forwarding network mail.

Third, the F= delivery agent flags also tell sendmail how this particular delivery agent behaves. For example, the F= delivery agent flag might specify that it perform final delivery or require that it preserve uppercase for usernames.

Many delivery agent flags have special meaning to sendmail; others are strictly user-defined. All the delivery agent flags are detailed at the end of this chapter (Delivery Agent F= Flags on ...