Here's an interesting tip from Prescott "Pete" Lustig, Senior Marketing Strategist at Loop Consulting Group:
An approach for attracting readers to your enewsletters --and getting people to read through them -- is an invitation to become an insider. Insiders get the useful information first. They get the facts that others don't yet have. They become, in effect, members of a private club.
In actuality, all readers of the newsletters become insiders just by opening them. But the strategy is to establish an identity for the letters as a source for exclusive information.
This works particularly well for financially-oriented newsletters. But it can also work for sports, entertainment (celebrity scoop), health, politics and more.
So, don't just lay the info out there. Enhance its value with an aura of exclusivity.