When you have a publicly known e-mail address featured on a corporate website, then sooner or later will start receiving spam. You can compare spam to the ads you receive in the analog mail, it looks like a letter and when you open it up it's advertising for some company. Spam is just that it looks like an e-mail from somebody and when you open it up it's an ad for Viagra or Ciales. A spam filter does for e-mail what I can not get done with analog mail, there is no spam bin in the analog email box where those envelopes can disappear into. This will filter out all or almost all spam from my e-mail boxes.