If you are getting 1000 visitors a day, and you are building a list, if you get 50 people on your list everyday, at the end of 3 months you will be having over 4500 people on your list and if you send a mail about your blog post to your list, you will eventually end up getting around 1500 additionally visitors to your 1000 daily visitors (if 30 percent visited) making it 2500 visitors for that day.