Hey guys, I can't use part milter macros such as $a, $b, $g, even if I let
$sender = $ctx->getsymval('g');
I got undef.

But some of those macros are avaliable, include: $_, $j, ${auth_authen} .... they works fine, they were all defined in sendmail.cf by default:

O InputMailFilters=ZackMilter
O Milter.macros.connect=j, _, {daemon_name}, {if_name}, {if_addr}
O Milter.macros.helo={tls_version}, {cipher}, {cipher_bits}, {cert_sub
+ject}, {cert_issuer}
O Milter.macros.envfrom= i, {auth_type}, {auth_authen}, {auth_ssf}, {a
+uth_author}, {mail_mailer}, {mail_host}, {mail_addr}
O Milter.macros.envrcpt={rcpt_mailer}, {rcpt_host}, {rcpt_addr}
O Milter.macros.eom={msg_id}
[download]

I've tried to write "g" into "envfrom=" line, like

O Milter.macros.envfrom= g, i, {auth_type}, {auth_authen}, {auth_ssf},
+ {auth_author}, {mail_mailer}, {mail_host}, {mail_addr}
[download]

$g still don't work, like $a, $b & some others.
In lines below of sendmail.cf, I found:

#########################
#   Format of headers   #
#########################

H?P?Return-Path: <$g>
HReceived: $?sfrom $s $.$?_($?s$|from $.$_)
    $.$?{auth_type}(authenticated$?{auth_ssf} bits=${auth_ssf}$.)
    $.by $j ($v/$Z)$?r with $r$. id $i$?{tls_version}
    (version=${tls_version} cipher=${cipher} bits=${cipher_bits} verif
+y=${verify})$.$?u
    for $u; $|;
    $.$b
H?D?Resent-Date: $a
H?D?Date: $a
H?F?Resent-From: $?x$x <$g>$|$g$.
H?F?From: $?x$x <$g>$|$g$.
H?x?Full-Name: $x
# HPosted-Date: $a
# H?l?Received-Date: $b
H?M?Resent-Message-Id: <$t.$i@$j>
H?M?Message-Id: <$t.$i@$j>
[download]

So I beleve $g, $a, $b has already defined, I wonder if they were disabled by default?
Is there something else I need to do for "enable" them?