It might seem a bit old fashioned...
but eMails are still an effective way to communicate with clients. The beauty of emails is that we can now monitor who has received them, who has opened them and read them, and also if they responded to the email. This allows for very accurate measurement of the email campaign and working out the how to continue forward. And the best part about emails is that they are free to send. Once you have a campaign designed, and set up to send, you just hit the send button. This makes them multiples cheaper than traditional print advertising, and you get feedback within a day or two about the success of your campaign with just the cost of preparing the email.
What should I say in my emails?
It depends on what you are trying to do. With a 'big picture' set of glasses on, you have to step back and work out where you want to steer your clients. Do you want them to buy something? Are you trying to tell a story and build up to a conclusion? Do you want to just develop a better relationship with them? There are so many ways to develop an email campaign as the 'cost' of the campaign is so much cheaper than print, radio or television advertising. The 'carry' of the ad is free, so this gives you a lot more room to move in how many times you are going to deliver your message and what you are going to say. And your 'print space' is free, so you can send a whole book through if that is what you want to do. You do have a constraint on the size of emails, as some servers will limit you to 5mb or so of data but that is not hard to work around if you think it through.