On one of my e-mail addresses (although not on any of the others) I am getting about 100 messages a day from mailer-daemon informing me that my outgoing e-mails are being returned undelivered. These would appear to be automatic responses to spam e-mails not e-mails I have generated.

I have run Norton security (including firewall, outgoing and incoming e-mail virus checking, files scanning etc) but this is clear.

Can anyone help? Firstly how do I stop this and is this doing harm other than being a nuisance.