The message 1236259880.3143.34.camel@ecrins.fosdick.home.net from Steve Fosdick lists@pelvoux.nildram.co.uk contains these words:
On Thu, 2009-03-05 at 09:01 +0000, Peter Alcibiades wrote:
I get an email apparently sent from my own address. For example, my address is, lets say, george@george.net The email as shown in the headers is as follows: (sparing you the men's health html content....)
I have had a few of these too.
Some spam filters have a whitelist of "trusted" addresses and any e-mail received from one of these addresses is assumed not to be spam without doing the other checks. I suspect the sender is hoping your own address will be on that whitelist.
With standard Internet e-mail anyone (who knows how) can send e-mail apparently from any address. Only by tracing the route by which it was delivered can one determine if it is likely to have come from the person who claims to have sent it.
And with malice, it can become a Joe-job...