hey john, i'm pretty sure what you mean is that you are getting emails that contain a link in them which then brings you to a website. many times its for online meds..make money from home programs..replica watches etc....
generally when you receive these the sender has no idea you ever got spammed (it doesnt even appear in their out or sent folder, because they arent sending it).
it happens a lot with yahoo accounts, aol and sometimes msn. what actually has happened is the persons contact list has been hijacked (for lack of a better term) and the email are being sent to each person from the contact list in the name of the person the list was lifted from.

for example if your contact list was stolen people could be getting emails from john@toplace (whatever your email is) and you wouldnt know until the person, your friend, family member etc told you