# Transactional email

*Marketing*. An email message sent in response to a user interaction with a web application.

A web application sends a transactional email to facilitate an agreed-upon transaction or update a customer about an ongoing transaction. It includes any email that a user triggers, including, but not limited to:

* Account Signup
* Password change
* Purchase Receipt
* Check-in
* Notification
* Friend or follower request

These emails contain information a user wants or needs. As a consequence, these emails have the highest [open rates][open-rate] across all categories of email.

Build email messages with a good visual, concise content, and appropriate headers.

[open-rate]: /docs/sendgrid/glossary/open-rate