I received an email from someone with my exact address-could the beta mail have caused it? and what can I do?

I temporarily changed to yahoo beta mail then went back to old mail sys. and found in the bulk mail a sender with my exact address. I have an ATT yahoo address, but still use this address as my friends are used to it. My system is also much slower since I dared try beta mail, which was impressive, but unfamiliar. I hope no one else has my I.D. as I have folders with personal business in them. Please help me if you can. Thank you