Executive Summary: How Solidrix Send handles high-volume transactional email delivery with dynamic provider failover, bounce parsing, and webhook callbacks.

Transactional email deliverability (password resets, OTPs, invoices) directly impacts business operations. Relying on a single SMTP gateway creates a single point of failure if the provider experiences downtime or IP throttling.

1. Multi-SMTP Router Architecture


In Solidrix Send (https://send.solidrix.com/), we built an intelligent routing engine that distributes email dispatches across multiple tier-1 SMTP providers (Amazon SES, SendGrid, Postmark, Mailgun):

1. Provider Health Scoring: Monitors live delivery success rates, bounce rates, and latency for each configured SMTP channel.
2. Automatic Dynamic Failover: If Provider A returns a 5xx error or connection timeout, the email is instantly re-routed through Provider B without dropping the message.
3. Queue Processing with Redis: Incoming HTTP API dispatch requests are acknowledged immediately with a UUID tracking token and queued in Redis for async delivery.

2. Webhook Ingestion & Real-Time Event Tracking


Delivery status notifications (Delivered, Bounced, Opened, Spam Complaint) are parsed via incoming webhooks from each provider:

  • Normalized event payload structure across different provider formats.

  • Real-time notification dispatched back to client webhooks using exponential backoff retry algorithms.

  • Automatic suppression list management to prevent emailing addresses that generated hard bounces.


    • 3. Results Achieved


  • 99.99% Inbox Deliverability SLA

  • Average Email Dispatch Latency < 450ms

  • Zero Single Point of Failure for Critical SaaS Transactional Emails