Even with junk mail filters spam has a way of seeping into our lives. The spam filter can be a detriment to those who are interested in taking free online surveys.
It's hard to trust the ones that have wound up in your inbox unannounced. More often than not they turn out to be scams. So if you do want to take a legitimate survey you will have to seek them out. One way to do this is going to the site itself that offers the survey. If they are not administering surveys at the time you can join what is called a survey panel -- their emailing list. When something does come up they'll send you an email invitation with a link to the free online surveys.