Postmark is a transactional email platform for web apps. And Rebound lets Postmark customers embed javascript into their web app so that they can notify their users about potential email delivery issues.

Chris Nagele, Co-founder & CTO at Wildbit, came up with the idea to let Postmark customers notify their users about email delivery issues directly from their own web app. I jumped at the chance to work on it during a hack week, and from that came Postmark Rebound.

When an email hard bounces in Postmark (due to reasons like invalid addresses, blacklisted IPs, etc), the email address is deactivated to prevent further emails from being sent. This helps protect against abuse while maintaining Postmark’s reputation with major email service providers. If it’s a temporary issue like a full inbox, it likely means the email address is valid and the recipient still wants to receive emails. So Rebound’s goal is to notify these users so they can update their address or contact support to resolve the issue.

Customization & Setup

I wanted the setup process to be quick and easy by providing a few pre-baked options, but still flexible for those who prefer a deeper integration. It also includes an API event hook for those that prefer to use their own UI.

The message fields support markdown formatting and dynamic variables from the mail server. This way users know exactly why their email address was deactivated.

The setup options generate a custom javascript snippet that’s ready to be integrated into a web app.

For those that prefer a deeper integration, Rebound also includes a javascript API.