The text discusses the importance of transactional emails, which often have high open rates compared to marketing emails. It highlights five best transactional email services: SendGrid, Mailchimp Transactional Email, Postmark, MailerSend, and ZeptoMail. Each service has its strengths and weaknesses, such as ease of setup, customer support, customization options, deliverability, and pricing. The article provides in-depth reviews of each service, including their features, pros and cons, and pricing plans. It also offers suggestions for choosing the best transactional email app based on individual needs and workflow preferences.