Making sales is incredibly important for your company, and making money is the bottom line. However, even though you think you might be able to make a quick buck off of a promotional email, you’ll make much more in the long run if you focus on the customer more than you focus on the sale.
Don't Make All of Your Emails Sales Focused
People don't sign up for your email lists because they want to listen to you promote your own business. They sign up because they want to learn something valuable from you and your company (and occasionally because they want to get discounts, too). While your email list can serve as an important sales tool, your emails should not all be about promoting or selling something to your customers. If your emails are valuable in other ways, a lot of the time they make sales on their own without the promotion. Focus on helping people before you focus on making a sale or two.
Stop talking about your services and start talking about your customers. They have issues, and you should be in the business of solving those issues - not in the business of trying to get them to buy something. Do that and you'll see that people begin to trust you, and that will make them more inclined to share with other people and buy when they're ready to buy, too. There are tons of companies that do a great job of showing people this. The companies that do successful email campaigns send out emails that sound like one-on-one conversations instead of promos. Sign up for some of these lists - those you know are successful - and see what they do that you don't.