how can I stop emails where recipient is blank ?

I have succesfully set up account level filtering but can't seem to filter out emails which have no recipient address. I notice some junk emails have To: undisclosed-recipients and have created a filter for that but with the junk mail below there doesn't seem to be a "To:" . To be honest I don't understand why spam assassin doesn't pick it up . If there is no recipient in the header I would have thought it is an obvious junk mail ---- Return-path: Envelope-to: [email protected] Delivery-date: Tue, 26 Jan 2016 04:27:52 -0500 Received: from mx4.enmail.com ([162.243.5.151]:43702) by ecbiz153.inmotionhosting.com with esmtp (Exim 4.85) (envelope-from ) id 1aNzui-0003SM-2W for [email protected]; Tue, 26 Jan 2016 04:27:52 -0500 Received: (qmail 7868 invoked by uid 0); 26 Jan 2016 09:27:46 +0000 Received: from unknown (HELO localhost) ([email protected]@120.62.185.61) by 0 with ESMTPA; 26 Jan 2016 09:27:46 +0000 x-onsmtp:0:1969306642:120.62.185.61:[email protected]:[email protected] Date: Tue, 26 Jan 2016 09:27:36 +0000 From: Aron Brock Subject: Refund for the Purchase - Aron Brock MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----------145380045656A73C0841AEC" X-Spam-Status: No, score=2.3 X-Spam-Score: 23 X-Spam-Bar: ++ X-Ham-Report: Spam detection software, running on the system "ecbiz153.inmotionhosting.com", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see root\@localhost for details. Content preview: We are very sorry to inform you, however, the unit you have ordered is out of stock. In the document attached you can see the details about the cancellation policy. [...] Content analysis details: (2.3 points, 4.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 1.0 MISSING_HEADERS Missing To: header 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% [score: 0.5743] 0.5 MISSING_MID Missing Message-Id: header X-Spam-Flag: NO ------------145380045656A73C0841AEC Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit We are very sorry to inform you, however, the unit you have ordered is out of stock. In the document attached you can see the details about the cancellation policy.