Postmark, an email service provider, has introduced a new approval process for new customers to ensure the best inbox rates and delivery speeds. The company believes that transactional emails are different from general emails and require manual vetting to guarantee deliverability. The new sign-up process will manually review accounts to verify that they share Postmark's values of sending high-engagement, transactional emails as part of their business infrastructure. This change aims to maintain the company's reputation for reliability and deliverability while providing exceptional service to its existing customers.