A definitive guide
Transactional emails are automated emails sent on a one-time basis, usually triggered by a user interaction or system change on a particular website or application. They are typically sent to one person at a time, and contain important, useful or actionable information that relates directly to the service or activity involved.
Typical transactional email types include account notifications, receipts for online purchases, invitations, support ticket updates, password reset notifications, magic sign up links and many, many more.
Transactional Emails are distinctly different from Marketing, Bulk or Mass emails. Marketing emails are sent in bulk to different cohorts (groups) of customers, with the aim to drive customers to a particular call to action. Transactional emails are usually only sent to one person at a time, and have a specific purpose based around the service being offered.
Because most users want to receive transactional email, they tend to have a very high read rate, and a low spam score. This in contrast to Marketing emails which have very low read rates and are often marked as spam. As such, you should never mix them up, always keep them separate and ideally send through two different services to ensure your transactional email read rates and spam scores are not affected by marketing campaigns.
There are many transactional email types, here's a short list of examples:
Of course there are many, many more
Transactional emails are often used for activities that require an immediate response (e.g. account verification) and therefore need to arrive quickly. In many cases users expect transactional emails to land in their inbox almost instantly, and it can be real detraction to customer confidence when they don't. If you've ever had to wait a few hours for a receipt for an online purchase, you will know exactly why.
At OhMySMTP.com we measure, track and optimize for time to inbox. We publish live results on our landing page for all to see to hold ourselves accountable to our fast transactional email delivery times.