The chances are that a spammer, or someone operating a phishing site is forging your E-Mail address onto his to avoid beiing identified, and to avoid all those bounced mails cluttering up his E-Mail account.
There is really nothing you can do to stop this. However, what I would recommend is having more than one E-Mail account. I have 1 I use for work, contacting government agencies etc. I don't give that address to very many people. I have another that I use for most of my everyday needs, and yet another I use if I am the least bit dubious about the person/organization. I really don't care about what happens with or to the third account.
