Why do people have servers that send email from invalid domain names?  This is worse than a spammer who PRETENDS to be from another domain name; you're sending from a domain that doesn't even exist, and has no MX servers registered in DNS.  How is a server supposed to realise that emails coming in are legit?

Spam filters are put in place for a reason.  If you want your emails to be delivered and read, you should probably send them from a domain with the correct SPF headers in place.  Emails that go missing like this are impossible to find again. 

Typical header set: (3 different emails)

Return-Path: <PB_eRecruiting@invalidemail.com>
Received: from nyrelay.<removed>.com (nyrelay.<removed>.com [<ip removed>])
        by [removed] with ESMTP id [removed];
        Mon, 03 Apr 2006 20:34:12 -0700 (PDT)
Received-SPF: neutral ([removed]: [removed] is neither permitted nor denied by domain of PB_eRecruiting@invalidemail.com)
Received: from nyprap28.ny.rsft.net (localhost.localdomain [127.0.0.1])
        by nyprap28.ny.rsft.net (Postfix) with ESMTP id [removed]
        for [removed]; Mon,  3 Apr 2006 23:34:12 -0400 (EDT)
Message-ID: <[removed].JavaMail.rsoft@nyprap28.ny.rsft.net>
Date: Mon, 3 Apr 2006 23:34:12 -0400 (EDT)
From: Pitney Bowes eRecruiting Center <PB_eRecruiting@invalidemail.com>
To: [removed] <[removed]>

Return-Path: <hr-ibm@invalidemail.com>
Received: from nyrelay.<removed>.com (nyrelay.<removed>.com [ip removed])
        by [removed] with ESMTP id [removed];
        Tue, 14 Mar 2006 15:50:29 -0800 (PST)
Received-SPF: neutral ([removed]: [removed] is neither permitted nor denied by best guess record for domain of hr-ibm@invalidemail.com)
Received: from nyprap09.ny.rsft.net (localhost.localdomain [127.0.0.1])
        by nyprap09.ny.rsft.net (Postfix) with ESMTP id [removed]
        for [removed]; Tue, 14 Mar 2006 18:50:29 -0500 (EST)
Message-ID: <[removed].JavaMail.rsoft@nyprap09.ny.rsft.net>
Date: Tue, 14 Mar 2006 18:50:29 -0500 (EST)
From: IBM Canada <hr-ibm@invalidemail.com>
To: [removed] <[removed]>

Return-Path: <hr-telusmobility@invalidemail.com>
Received: from sjrelay.<removed>.com (sjrelay.<removed>.com [ip removed])
        by [removed] with ESMTP id [removed];
        Thu, 26 Jan 2006 21:58:51 -0800 (PST)
Received-SPF: neutral [removed]: [removed] is neither permitted nor denied by best guess record for domain of hr-telusmobility@invalidemail.com)
Received: from sjprap06.sj.rsft.net (localhost.localdomain [127.0.0.1])
        by sjprap06.sj.rsft.net (8.11.6/8.11.6) with ESMTP id [removed]
        for [removed]; Fri, 27 Jan 2006 00:58:50 -0500
Message-ID: <[removed].JavaMail.rsoft@sjprap06.sj.rsft.net>
Date: Fri, 27 Jan 2006 00:58:50 -0500 (EST)
From: Human Resources <hr-telusmobility@invalidemail.com>
To: [removed] <[removed]>