More Hacking amavisd $msginfo

Hi,

I'm trying to find or develop a way to quarantine mail from specific
senders for specific domains. Is there a well-defined way to do this?
It appears the amavisd.conf doesn't provide the ability to specify
different policies based on domains.

So eleven years ago(!!!) I posted this somewhat related question:
https://lists.amavis.org/pipermail/amavis-users/2011-June/000503.html

Is it possible to use the $msginfo structure to inspect the different
headers and somehow make a policy decision on whether to quarantine an
email there? In other words, if I built a custom hook using the
$msginfo structure, and found one of the senders I wished to block,
based on the recipient domain, could I quarantine it from there?

I don't have an answer for what to do if a sender is on the blocklist
for one domain and not on another. I hoped it could be decided in a
per-recipient basis.

Here's (most) of the contents of my custom.conf.
package Amavis::Custom;
use strict;
use warnings;
#use diagnostics;
no warnings qw(uninitialized redefine);

# needed for write_to_db()
use DB_File;
use IO::File;
use DBI qw(:sql_types);
use DBD::mysql;
BEGIN {
  import Amavis::Conf qw(:platform :confvars c cr ca $myhostname);
  import Amavis::Util qw(do_log untaint safe_encode safe_decode);
  import Amavis::rfc2821_2822_Tools;
  import Amavis::Notify qw(build_mime_entity);
}

sub new {
  my($class,$conn,$msginfo) = @_;
  my($self) = bless {}, $class;
  my($mail_size) = $msginfo->msg_size;   # mail size in bytes
  my($mail_size_mb) = $mail_size/(1024*1024);
  my($hdr_edits) = $msginfo->header_edits;
  $hdr_edits->add_header('X-ActualMessageSizeBytes', $mail_size);
  $hdr_edits->add_header('X-ActualMessageSize',
                         '*' x ($mail_size_mb > 50 ? 50 : $mail_size_mb));

  $self;  # returning an object activates further callbacks,
          # returning undef disables them
}

sub before_send {
  my($self,$conn,$msginfo) = @_;

  my($loc_subj)         = $msginfo->get_header_field_body('subject');
  my($loc_from)         = $msginfo->get_header_field_body('from');  #
raw full field
  my($loc_recip)        = $msginfo->get_header_field_body('recip_addr_smtp');
  my($loc_recip_final)  = $msginfo->get_header_field_body('rfc2822_sender');
  my($loc_to)           = $msginfo->get_header_field_body('to');  #
raw full field
  my($loc_sender)       = $msginfo->sender;  # envelope sender
address, e.g. '[email protected]'

  ...
}