Transactional email is a type of automated, non-promotional email that is triggered by events, interactions, or preferences within a service and is delivered to individuals one at a time. It contains user-specific content and differs from marketing emails, which are mass distributions of the same message to many recipients simultaneously. Transactional emails serve various purposes, including managing user accounts and logins, payment processes, specific events, delivering requested content, and providing updates on product usage. To send transactional emails effectively, businesses need a trustworthy provider with excellent deliverability, and resources such as email design guides, best practices, and templates can be helpful in creating beautiful and effective transactional emails. Postmark is a reputable transactional email service that delivers emails to customers on time, every time.