If you've come to this site because you got a spam message from someone at timt.net, I'm sorry. I'm as much a victim of this as you are. Some waste-of-flesh spammer is spoofing my domain. I get hundreds of bounce messages every day. I can only imagine how many messages are actually getting to people's inboxes without a bounce.
I've looked into using SPF, but have not figured out how to implement it with my current provider's set up. In any case, it would only help when the spammer sent a message to a mail server that checked the SPF record on the purported sending domain. I think the number of sites that check this are still few.
Perhaps some day we'll have a different email protocol that will fix this....