--- a/man/procmail.man
+++ b/man/procmail.man
@@ -723,6 +723,15 @@
 .fi
 .ad
 .PP
+Some mailers (notably exim) do not currently accept the above syntax.
+In such case use this instead:
+.PP
+.na
+.nf
+|/usr/bin/procmail
+.fi
+.ad
+.PP
 Procmail can also be invoked to postprocess an already filled system
 mailbox.  This can be useful if you don't want to or can't use a
 $HOME/@DOT_FORWARD@ file (in which case the following script could
