Everything on an email should encourage the reader to click through to finalise the deal. The headline, the headings and all the graphics should concentrate on that. Anything else is a distraction. How can the copy help?
An appreciation of the fact that if a recipient goes on to read the body of text on an email it has failed will show you the direction to take when considering what to include. It is like a long stop in cricket, there to snare the ones who sneaked through.
If they get as far as the copy the reader is interested but not convinced. You might think overwhelming them with masses of detail might be best but take care.
You must give them the information they require. Too little and they will not read, to much and they will close the email. It is a balance.
The first essential of direct email marketing is to explain the offer. If it is, for instance, a golfing holiday, then point out the most saleable features: the courses, the professional, the weather. If it is the other type of course, one where you are taught something useful, then give the prospectus or, if you have a celebrity facilitator, name them.
Go on to explain in more detail the benefits of the product: faster delivery, better detail, unrivalled reliability. If it scored nearly 100% in some review, say so.
But there is always a but. You must do this in just a few sentences. The optimum is two under each headline. If the product has a technical side then provide a hotlink to a specifications page, the sort of things that even those who click through do not fully understand. Keep it out of the email proper.
All marketing emails should be a whole so finalise the offer by giving a closing summary. Build it up, perhaps by saying that they will not be able to find similar quality at such a reasonable price elsewhere. Remember that although still interested the reader has not conformed to your intentions. Many suggest some kind of signature. You know the make-up of your email list best so the decision is down to you.
If they still want to read on then you are in trouble. However, it costs nothing to have an overview of the offer and its benefits: a précis just in case.
All that remains is for the information that you must include to comply with the law, such as your company details and the method of unsubscribing.
Some take this opportunity to include their full privacy statement but this is not required. Include a hotlink to it with some reassuring text. Tell them that not only do you comply with all the provisions of the law but go further.
In email marketing the copy requirements are unique. You hope it will not be read. Indeed if it is then there is something wrong with the rest of the email. However, if it is precise and targeted anyone who reads that far is still available. Go get them.