An email list is a collection of email addresses that enables users to send the same email message from a central postbox to any number of Internet users. Companies use email lists to market, cross sell and up-sell, and to build customer relationships over time. Email lists can be purchased or put together manually. A permission-based email list that you built yourself is refereed to as a house list. Your house list is one of your most valuable assets because it is 7 times less expensive to market to an existing customer than it is to purchase one. MyNewsletterBuilder (MNB) provides tools to organize and segment multiple email lists under different categories. MNB also provides webinars and tutorials on how to expand your email list.