Addressses added to my mail

I am new to Mac, about a week, and just noticed when I typed in the first couple of letters of an email address the auto fill took over OK, but found that I had about a half dozen address pop up as options on my email, that are not in my address book. Where did they come from? One was for a Toshiba laptop address and one was a viagra address.
Suggestions please. I looke under email preferences but don't find any clue there.

Thanks,
Ken