The priorities for email communication depend on your business strategy and goals. With that said, I believe you should begin with your customers and you should create an email marketing focused on retention and engagement objectives. Established customers are your most valuable audience since they have already expressed interests in your products and services they should be open to regular communications. You've earned trust and email provides a cost efficient way to communicate relevant and valuable information. Email campaigns, like product promotions and scheduled sends, like company newsletters to this audience will help enhance their engagement with your business and maximize their lifetime value. The relevancy of the content key to the success and planning these campaigns around user defined preferences is a suggested approach.

A secondary objective of email would be to enhance customer acquisition and nurturing of leads through a sales funnel. This is could be a campaign to educate the audience on a particular product feature or service in a long considered purchase process. Alternatively it could be a promotional incentive to prospective customers who abandoned their online shopping cart in a retail purchase. The content strategy here is to provide information and incentives to help overcome buyer objections.

The last and most controversial use of email is unsolicited bulk email to individuals who have no prior relationship to your business. Like cold-calling, this strategy is used to initiate an interaction with potential customers. This is generally done via affiliates who offer list rental services to databases that have opt-ed in to receive offers from 3rd parties. Some businesses actually acquire lists and do mailings themselves. Buyer beware as there is lots of risk around this strategy as it is considered SPAM.

Hope this helps. If you have some more information about your business and objectives, we can go into more detail. Good luck.