Milter-greylist

> Unless a m4 expert step in, I'm going to just fix the documentation by
> adding a warning.

I'm not an expert in m4 either, but I use m4 frequently to build the .cf
files...

Sendmail 8.13.7 (I guess all sendmail 8.13.X) defines these
milter-macros by default, after you add the INPUT_MAIL_FILTER()
statement in the .mc-file and rebuild the .cf-file using m4:

O Milter.macros.connect=j, _, {daemon_name}, {if_name}, {if_addr}
O Milter.macros.helo={tls_version}, {cipher}, {cipher_bits},
{cert_subject}, {cert_issuer}
O Milter.macros.envfrom=i, {auth_type}, {auth_authen}, {auth_ssf},
{auth_author}, {mail_mailer}, {mail_host}, {mail_addr}
O Milter.macros.envrcpt={rcpt_mailer}, {rcpt_host}, {rcpt_addr}
O Milter.macros.eom={msg_id}

(Sendmail 8.11.x and 8.12.x may vary...)

That's enough to get milter-greylist running (with a basic
configuration).
I recommend using the generated defaults (and not playing with
milter-greylist.m4, if don't know what you are doing). There are many
other milters need some of those macros defined by default (eg.
clamav-milter).

Macros missing from milter-greylist.m4 is:

 {verify} in Milter.macros.helo and
 {greylist} in Milter.macros.envrcpt

Those two are not needed by default (unless you use special setup for
whitelisting verified TLS-connections and whitelisting in access(db)).
(See the milter-greylist README for more info on that...)

/P