How Can I Track Down Spammers Who Use My Domain Name To Send Emails?

There isn’t much you can do about it except use as tight a security as possible. Use an encrypted form of security on any wireless connection, utilize electronic verification that it is you who are sending out email, giving the recipients the public key, while you keep the private key, use a firewall, and keep your passwords and user names secret. You can also delete any mail you are not expecting, or don’t know the sender, without opening it.
These spammers use web beacons to alert them when an address is viable. If a user opens the email, the web beacon sends a signal to them which shows that address has activity, marking it as active. That email then receivies a barrage of spam.
Also, don’t use the normal format of emails, first initial, last name, or last initial, first name. Spammers use these computer programs to spew out addresses based on phone books and dictionaries, as they know most business use the first/last format for addresses and user names on accounts.
Use a commercial grade firewall/anti-virus and spyware/malware application too. I would use a router even if I didn’t use wireless due to the strong MAC address filtering it offers. Any MAC address not on my Allow list does not get onto my network, or past my hardware firewall.
Even with these precautions it will be difficult at best to stop spammers. They are becoming ever bolder and more technologically savvy as time goes by. They are ramping up their efforts and it is just getting out of hand.
The email precautions are the best ways of circumventing them, however. If they don’t have your addresses, they can’t send spam to you, or use your domain to send out spam.
You can look at the full header view to get an idea of the route the email came from, but it only gives a few points, not all the routers and servers it went through to arrive at your door. I would install a really good anit-spam program on my client based email programs too.