Postmark is a transactional email service provider known for its exceptional deliverability and reliability. Founded in 2009 and later acquired by ActiveCampaign, Postmark focuses exclusively on sending important application emails like password resets, receipts, and notifications.

Unlike traditional marketing ESPs, Postmark specializes in transactional and triggered emails that require immediate and reliable delivery. The platform is designed for developers and technical teams, offering robust APIs, comprehensive documentation, and developer-friendly tools for monitoring and troubleshooting.

Postmark provides detailed delivery analytics, bounce handling, spam complaint tracking, and DMARC monitoring. Its emphasis on maintaining a pristine sending reputation by enforcing strict sending policies has made it a preferred choice for businesses that prioritize deliverability over high-volume marketing campaigns.

The service is particularly popular among SaaS companies, e-commerce platforms, and financial services that require guaranteed delivery of critical communications. Postmark's transparent approach to deliverability, combined with its specialized focus on transactional email, distinguishes it from broader marketing automation platforms.