Many email newsletter software vendors offer transactional email support, which gives companies the ability to include promotional messages within the body of transactional emails. There are also software vendors that offer specialized transactional email marketing services, which include providing targeted and personalized transactional email messages and running specific marketing campaigns (such as customer referral programs).
Transactional or relationship email messages complete, confirm, or provide information about a previously agreed upon transaction. In the ecommerce context, transactional emails most often include order confirmations, shipping notices, and invoices. Email responses to other "transactions" like newsletter subscriptions or entering a contest also fall into this category.
Transactional emails are important. Customers expect a confirmation that an order has been received and are eager to learn when an order has been shipped. These emails frequently enjoy an open rate twice that of purely marketing emails and, according to email service provider Silverpop, can have click-through rates above 20 percent.