I read that you opened an attachment on the email. I would immediately run a virus and spyware scan on your entire computer! Attachments from unknown sources are how worms, viruses, and spyware are spread.
~adknight
My first thought was "don't open attachments from people you don't know"...look out spam and viruses.
Hopefully that is not the case, after all.
Good luck and thanks for sharing your stress so that we can learn and benefit too!
Bless your heart darlin..... Sleep well tonight 
I would not send anything by email...wait for the hard copy and then call the law firm to confirm the lawyer is working on the case and talk directly to that person.
Any one can look up a legit name on the computer and use it for ill.
Please be careful on this and I am glad that you will be able to sleep better tonight.
Please stop emailing this person. For something as serious as this I think that a phone call and a certified letter would have to do. You need evidence of all verbale and written transactions between the two of you. Check you computer for viruses. Do not give out any personal information about you or your friends. If they are serious and this is a real legal office they will already have your personal information. And as far as the copyright laws, yes they suck and 3/4 of the cakes on here are probably illegal in some way. Will that stop people from making cakes the way their customer wants. Probably not. It would be a very scary situation for any person if they had go to jail or pay a fine because they decided to make a frozen buttercream transfer of mickey mouse. 
Please stop emailing this person. For something as serious as this I think that a phone call and a certified letter would have to do. You need evidence of all verbale and written transactions between the two of you. Check you computer for viruses. Do not give out any personal information about you or your friends. If they are serious and this is a real legal office they will already have your personal information. And as far as the copyright laws, yes they suck and 3/4 of the cakes on here are probably illegal in some way. Will that stop people from making cakes the way their customer wants. Probably not. It would be a very scary situation for any person if they had go to jail or pay a fine because they decided to make a frozen buttercream transfer of mickey mouse.
My company does regular searches for use of our logo, and our lawyer immediately send cease-and-desist letters to anyone who's using it. It does not matter one bit if someone is trying to make money off it; it's our logo, and it's not allowed to be used by anyone but us. As long as they take it down immediately, we don't do anything else, though.
I'm glad your situations seems to be working out!
I woudn't wait for a certified letter, I'd be calling the lawer now to see if it's legit and I would not be answering any emails under any circumstances. If it's not legit the lawyer may want to do something about this person using his/her name and you could supply them with the IP address from the emails you have received.
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