mailer deamon never ever run on your computer. It only run on servers that need to process e-mails, like web mail providers, your ISP, most corporate servers.
Your problem is that some spammer is sending spammy e-mails that PRETEND to be comming from you.
There is ABSOLUTELY NOTHING wrong on your side.
Some advices:
NEVER EVER post your actual e-mail address on any forum, comment sections, guess book, and social networks.
NEVER EVER propagate any chain e-mails, and ask all your contacts to do the same.
If you receive a chain e-mail, it may be good to delete all present content and reply to all asking them to never forward those, ever.
Ask all your contacts to make sure that their computers are virus and spyware free.
Electro, February 2012