Blank emails

[Peter Bishop]

On 10 Jun 2004 at 22:40, Tom Allison wrote:

> I don't know if you can do multiple regex header checks  in one line 
> with postfix, but you could always do the logical NOT regex tests like
> this:
> 
> If Subject: does not match "" then OK
> If From: does not match "" then OK
> If To: does not match "undisclosed recipients" then OK
> else REJECT
> 
The actual blank email header looks a bit like this:

Delivered-To: <pgb at adelard.com>
Date: <valid_date>
From: <the_spammer>
Message-Id: <valid_message_id>
Received: <some_random_string>
Bcc:
Status:  

The header is terminated by two returns but there is no body text at 
all.
So there is no Subject line, and no proper To line (just a Bcc)

So I guess the lack of a Subject line might be sufficient to detect 
such probes.
"Proper" emails should have a Subject line - even if the sender 
forgets to fill it in.

-- 
Peter Bishop 
pgb at adelard.com
pgb at csr.city.ac.uk