The article compares seven popular SMTP email services: Postmark, Sendgrid, Mailgun, MessageBird (formerly SparkPost), Amazon SES, Mailchimp Transactional (formerly Mandrill), and Brevo (formerly Sendinblue). The guide helps users evaluate the best SMTP service for their sending needs by considering factors such as email deliverability, ease of setup, documentation, customer support, price, tracking capabilities, data retention, security, and other key qualities. Each service is analyzed in detail, including its pros and cons, pricing, and features. The article also provides a comparison spreadsheet to help users choose the most suitable SMTP service for their needs.