Include a Call To Action
Although not every email is about selling something, there should be a clear goal or purpose of the email. This Call to Action should be connected to your subject line in some way. For Example, you could add a link to your website, blog, Facebook, etc that your reader could go to see more information and make an action based on the email.
When writing an email, there is no need to change your writing style as if you were writing a textbook. Instead, you should communicate as you would in a casual conversation. A good test is to read the email to yourself aloud to see how it sounds.
Keep Your Message Simple
Keeping your readers engaged is vital in order to prevent your emails from being deleted. Successful emails should not be unnecessarily wordy or complicated. Keep in mind that you have high competition for your readers' attention.
Be A Resource
In order to gain your readers' respect, you need to provide valuable information, whatever that may be. Readers will quickly loose interest if your emails become predictable or lack useful information.