Mailgun Push

Transactional notification pipelines have a habit of silently failing, messages that appear sent but never arrive. I built this to handle the reliability edge cases.

A transactional email and push notification service integrating Mailgun across product alerts, digests, and user communication workflows. Engineered to handle the delivery edge cases that cause notification pipelines to silently fail.

Transactional notification pipelines have a habit of silently failing in production, messages that show as 'sent' in your dashboard but never arrive in an inbox. The failure modes are well-documented: ISP filtering, webhook delivery gaps, retry storms, and the quiet drop that happens when a bounce isn't handled correctly. This project builds a reliable transactional messaging service on top of Mailgun, engineered specifically to handle the edge cases that cause pipelines to fail silently.

1. 1.
   Reliable Email Delivery: Integrate Mailgun with retry logic, bounce handling, and delivery status tracking, so failures are visible before users report them.
2. 2.
   Push Notification Delivery: Extend the pipeline to push notifications across mobile and web channels, with the same delivery reliability standards as email.
3. 3.
   Observability: Build delivery observability into the system from the start, not as an afterthought, so delivery failures appear in dashboards rather than support tickets.
4. 4.
   Failure Recovery: Implement failure detection and automatic retry with exponential backoff, handling the transient failures that cause permanent drop in naive implementations.

• ◆
  Failure Mode Catalogue: Documented the 12 most common transactional email failure modes from production incidents and Mailgun's own documentation before writing any integration code.
• ◆
  Webhook Handler Design: Built robust webhook handlers for Mailgun's delivery events, delivered, bounced, complained, dropped, with idempotency keys to prevent double-processing.
• ◆
  Retry Architecture: Implemented exponential backoff with jitter for transient failures, with dead-letter queue handling for messages that exceed the retry budget.
• ◆
  Delivery Dashboard: Built a lightweight delivery status dashboard showing per-message delivery state, bounce rates by domain, and alert thresholds for anomalous failure rates.

A notification system that crashes visibly is easy to fix, you see the error, you fix the error. A notification system that silently drops 3% of messages is much harder to detect and much more damaging, because it erodes user trust gradually and invisibly. The observability design in this project treats 'delivered' as a claimed state that requires positive confirmation from the receiving mail server, not just 'we called the API and got a 200'. Every message is tracked through its full lifecycle until confirmed receipt or terminal failure.

Silent notification failures are invisible to most product metrics until a user complains. I designed observability into this from the start, not as an afterthought.

Delivery lifecycle tracking with bounce handling and dead-letter queue for messages exceeding retry budget.