Your .mc file must start with exactly one
OSTYPE() macro, which tells m4 what platform
you're running so that it can fetch the appropriate defaults from the
cf/ostype/ostype.m4 file. For example, if you say
OSTYPE(linux), m4 will read the file
You can use zero or more define() directives to set
variables which control the operation of the configuration macros. The
Normally, both the variable and the value are quoted as shown to
prevent their expansion by m4 itself.
Zero or more FEATURE() macros can be used to select
which special features your configuration will use or support.
One or more MAILER() macros must be used to define which
MDAs are used by your configuration. Usually, you only need to define
the local MDA and the SMTP MDA, like this: