Users have highly emotional reactions to newsletters. This is in strong contrast to studies of website usability, where users are usually much more oriented towards functionality. Even a website that you visit daily will feel like a tool where you simply want to get in and get out.
The positive emotional aspect of newsletters is that they can create much more of a bond between user and company than a website can. The negative aspect is that usability problems have much stronger impact on the customer relationship than they normally do.
Users spend 51 seconds reading the average newsletter. The layout and writing both need superb usability to survive in the high-pressure environment of a crowded inbox.
Averaged across our study, newsletters lost 19% of potential subscribers due to usability difficulties in their subscription processes and designs. People often stay subscribed to newsletters they don't want (cursing the sender with every new issue that clutters their inbox), so the unsubscribe process is also worth improving.
Newsletters need to be smooth and easy: they must be seen to reduce the burdens of modern life. Even if free, the cost in e-mail clutter must be paid for by being helpful and relevant to users - and by communicating these benefits in a few characters in the subject line.