What does it mean to block a subscriber?
Some people might send spam to your autoresponder, instead of emailing to request information. Not only is this annoying, but it can affect your statistics, which can throw off your marketing efforts.
Blocking a subscriber will prevent that email address from signing up to your leads list.
Why Would I Block A Subscriber?
One common use of blocking is keeping competitors off your list. You also may find that there are other people who, for one reason or another, you don't want to be able to receive your messages.