How to design a good email

It’s been a long time since I’ve designed an email, so before I start here are a few basic things that I should consider.

Designing the email

Who’s it for: While designing the email you should keep in mind who the target audience is. The email should be relevant and interesting to the reader, otherwise it will often be considered to be spam.
What do you want them to do: You should also think about what you want the reader to do once they have read the email, basically, what is the call to action. This should be simple for the user to find, so keep irrelevant copy and links to a minimum.
The layout: It’s very important that the reader immediately recognising who the email is from, so keeping the logo to the top left is a good idea. Also consider that the email will be viewed in different browsers and applications and may also be initially viewed in a preview pane. This means you should try to get the message across to the reader without taking up too much space. Think about how the content is set out. Titles should be short and informative, any images should be relevant to the content and try to be as concise as possible. Also minimise fonts, colours and images as these can make the email confusing and difficult for the reader to scan quickly. And finally, make sure the call to action is prominent in the email, so the reader can easily understand what the email wants them to do next.

The subject line: The subject line is the motivation for the reader to actually read the email, so it’s very important to get this right. You should briefly describe the emails’ content, and add something attention grabbing. It’s also a good idea to add a call to action whenever possible
Personalise: If you have a name associated with the email address it’s a good idea to use this in the email. It will help confirm that the email is not spam, and also make the reader think the email is more relevant to them, hence making it more likely to be read.
Talk to the reader: Copywriting is a skill all on it’s own, but quite often it will also be one of the designer’s tasks so it’s worth thinking about carefully. Try to think of the email as a conversation, rather than dry information and keep it simple and concise so the reader doesn’t have to read through lots of text to find out what the email is about.

Click, click, click: Make sure any images and relevant text are clickable; you want to give the reader as many opportunities as possible to click on the email.
Important links: There are a some additional links that should be on every email. Having an unsubscribe link is essential. It will reassure the reader and is also a legal requriement. Another good practice is to add a link to a web version in case the reader has problems viewing the email.
Compatibility and stuff: Finally, remember all browsers and applications have different rules for displaying backgrounds and images, so your email may not be viewed exactly how you want it to be. This means you should try to build the email as simply as possible, you should never use background images and all styles and colours have to be applied in the HTML rather than with external CSS.

I’m sure there are many more issues to be considered when creating an effective email, so perhaps try a few of these resources too.