This appears to be a very interesting case. There are a number of questions that need to be answered to identify a particular cause of action. One important question I would like to have answered is: Did the founder enter into your email to send the messages, or did he simply modify the content of your email to reflect a different message?
There are a number of options available to you in this circumstances. There is a potential for criminal charges. There are also a number of civil causes of action that should be explored.
One of the most important issues will be to identify and quantify your damages and determine whether pursuing a cause of action is economically viable.
Either way a crime has been committed. If someone used your computer (even remotely) without your permission that is a crime. If he is just altering his emails to make it look like they came from you, or altering emails you sent him to harrass you, that is very likely harrassment. You should contact your local police department and hire a lawyer to investigate suing the perpetrator once he/she is caught. It should be a relatively simple investigation for them - I handled a nearly identical case earlier this year. They can contact the guy with the emails and ask him to turn them over. They can also examine your computer to see if no such emails came from it, and can apply for a search warrant to seize his computer if he is uncooperative.
Steven F. Fairlie, Esq.
Fairlie & Lippy, P.C.
1501 Lower State Road, Suite 304
North Wales, PA 19454
voice: (215) 997-1000
fax: (215) 997-1777
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