Why did I recieve an email with no content no subject?

Properties are (xxx is intentional) :-

X-Apparently-To: xxxx@yahoo.co.uk via xxx.xxx.xxx.xxx; Thu, 06 Sep 2007

05:16:20 +0000

X-Originating-IP: [91.92.201.39]

Authentication-Results: mta135.mail.ukl.yahoo.com from=; domainkeys=neutral (no

sig)

Received: from 91.92.201.39 (HELO 91-92-201-39-ixtlan-systems.unitednet.bg...

(91.92.201.39)

by mta135.mail.ukl.yahoo.com with SMTP; Thu, 06 Sep 2007 05:16:20 +0000

Received: from unicorn.arkansas.net (helo arkansas.net.espressotop50.com

[82.44.248.209])

by hotmail.com with SMTP id 6[10

X-Antivirus: avast! (VPS 000773-0, 05/09/2007), Inbound message

X-Antivirus-Status: Clean

Why did I recieve an email with no content no subject?computer protection

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