By and large, people don't take email for their entertainment. In fact, most of them view email as a burden. Every message has to earn its way, and many of them are freeloaders and failures. When a customer asks for an order confirmation, it's an opportunity to finish the job with a smile, not a cross-sell.
Alertbox: Transactional Email and Confirmation Messages, 2008-Oct-20, by Jakob Neilsen.
A striking conclusion from the studies is that processing email is stressful. Users frequently told us that they were too busy to deal with certain email messages, and that they considered any fluff in messages a waste of time. ... Transactional email has three goals:
- Avoid being mistaken for spam.
- Be a customer service ambassador.
- Prevent customers from calling in. (In a good way!)