Whether you own the e-mail or not doesn't matter... someone intent on scamming others in your name can still put YOUR email (even the ones you use most often) in the From: area by forging the headers. It's sad that people are doing this in the reptile industry >.<
I believe forging headers is a federal crime though so if you have a suspicion of who it could be, especially if it happens again (and it appears to come from your e-mail), perhaps make a report to your local police station and/or the feds themselves.
Here is a resource for detecting fake headers:
http://www.rahul.net/falk/mailtrack.html
I searched the IP and it seems like that provider is used for a lot of unscrupulous activity. Makes me figure that they won't respond to any reports but it's always worth a try.