Why am I getting this email?

[Ravendas]

My exim queue is getting really huuuge (700kish), so I was perusing the queue looking at messages. Here's an example header:

1Jjei0-00007F-N7-H
root 0 0
<[email protected]>
1207764464 0
-helo_name XXX.XXX.XXX.87
-host_address 125.110.168.234.4082
-interface_address XXX.XXX.XXX.87.25
-received_protocol smtp
-body_linecount 24
-host_lookup_failed
YY [email protected]
NN [email protected]
NN [email protected]
13
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]

154P Received: from [125.110.168.234] (helo=XXX.XXX.XXX.87)
        by mysmtp.domain.name with smtp (Exim 4.50)
        id 1Jjei0-00007F-N7; Wed, 09 Apr 2008 13:07:45 -0500
142P Received: from dns430.yahoo.com.tw (dns430.yahoo.com.tw [65.127.157.166]) by  with SMTP id nlw11MXU982MZn5;
         Wed, 09 Apr 2008 22:06:45 +0400
075I Message-ID: <[email protected]>
038  Date: Wed, 09 Apr 2008 22:03:45 +0400
065F From: "�N�s�A�X�l���j�����v��A�ϥ�" <[email protected]>
069R Reply-To: "�N�s�A�X�l���j�����v��A�ϥ�" <[email protected]>
330T To: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], bon@ms1
2.url.com.tw, [email protected], [email protected], [email protected], [email protected], [email protected], 1716_3
[email protected]
028  Subject: �r�k�P����E���ʷR
018  Mime-Version: 1.0
086  Content-Type: multipart/alternative;
        boundary="--NextPart_5nr_gcxo_btzkfjiqctbwujf3"

I noticed 2 interesting things:
1. The helo_name is my server's IP
2. None of the To: recipients are my local domains.

So, why isn't mail like this being rejected?? Does it have to do with the helo_name? Is there any way to check the recipient list to make sure it can actually be received, and reject if it can't?

BTW, running Exim 4.69, Spamblocker 3.1.

Thanks!