What is Transactional E-mail?

Transactional email is a type of automated email between a sender and a recipient. It differs from promotional email in that transactional email is triggered by events, interactions, or preferences within a service or application rather than by a company’s marketing campaign.
The most well-known types of all transactional emails are receipts and confirmations. These occur after a transaction has taken place, which is why these types of emails are called transactional in the first place.