use strict;
use warnings;
use Data::Dump qw"pp";
use English;
 
my %HoA;
my @AoA;
 
while (<DATA>) {
  
  if (my ($id,$fromto)=/: (\w+): ((?:from|to)=<.*?>),/ ){
    $HoA{$id}=[$PREMATCH,$fromto,$POSTMATCH];
    @AoA[$.]=[$PREMATCH,$id,$fromto,$POSTMATCH];
  }else {
    warn "Couldn't parse <<<$_>>> at line $.";
  } 
}
 
pp(\%HoA);
pp(\@AoA);
 
__DATA__
Dec 8 08:49:21 b.mx.sonic.net sm-mta18242: jB8GnCuK018242: from=<cj@or
+eilly.com>, size=10731, class="0", nrcpts=2, msgid=<E4461FEB-1B74-461
+2-80DC-3A39B04D89B1@oreilly.com>, proto=ESMTP, daemon=MTA, relay=mwes
+t.oreilly.com 209.204.146.24
Dec 8 08:49:21 b.mx.sonic.net sm-mta18528: jB8GnCuK018242: to=<mkirk@c
+orp.sonic.net>,<dane@corp.sonic.net>, delay=00:00:00, xdelay=00:00:00
+, mailer=esmtp, pri=160731, relay=lds.sonic.net. 208.201.249.231, dsn
+=2.0.0, stat=Sent (jB8GnLpC004736 Message accepted for delivery)
[download]

both data-lines have the same ID so maybe you don't want a HoA but a AoA

OUTPUT:

{
  jB8GnCuK018242 => [
        "Dec 8 08:49:21 b.mx.sonic.net sm-mta18528",
        "to=<mkirk\@corp.sonic.net>",
        "<dane\@corp.sonic.net>, delay=00:00:00, xdelay=00:00:00, mail
+er=esmtp, pri=160731, relay=lds.sonic.net. 208.201.249.231, dsn=2.0.0
+, stat=Sent (jB8GnLpC004736 Message accepted for delivery) \n",
      ],
}
[
  undef,
  [
    "Dec 8 08:49:21 b.mx.sonic.net sm-mta18242",
    "jB8GnCuK018242",
    "from=<cj\@oreilly.com>",
    " size=10731, class=\"0\", nrcpts=2, msgid=<E4461FEB-1B74-4612-80D
+C-3A39B04D89B1\@oreilly.com>, proto=ESMTP, daemon=MTA, relay=mwest.or
+eilly.com 209.204.146.24\n",
  ],
  [
    "Dec 8 08:49:21 b.mx.sonic.net sm-mta18528",
    "jB8GnCuK018242",
    "to=<mkirk\@corp.sonic.net>",
    "<dane\@corp.sonic.net>, delay=00:00:00, xdelay=00:00:00, mailer=e
+smtp, pri=160731, relay=lds.sonic.net. 208.201.249.231, dsn=2.0.0, st
+at=Sent (jB8GnLpC004736 Message accepted for delivery) \n",
  ],
]
[download]

UPDATE: better add a chomp after the while ...

UPDATE: adding a space to the regex helps catching additional mailadresses   my ($id,$fromto)=/: (\w+): ((?:from|to)=<.*?>), /;

but be aware that you have to be sure about the format of your logs, otherwise you need a parser for mailadresses which isn't trivial