One additional comment: for your website make sure and install a roadblock/pop-up to encourage folks to give you their email address when they first visit the website. Other optimization strategies for your website really depend on what type of site you have (ecommerce, general marketing etc.) For example, if ecommerce use tools to get people to give you their email address on the product details pages (i.e. a favorite or share via email to a friend option) since most ecommerce sites see over 40% of their traffic sources and come in on their product pages. For general marketing sites you can consider things like using email sign-up as a roadblock for downloading some sort of white paper etc.