Implementing Reliable Email Sending with RabbitMQ in Spring Boot

The tutorial walks through a complete solution for sending emails through RabbitMQ, starting with an overview diagram that illustrates the flow from message production, broker confirmation, consumer processing, to retry handling.

Implementation steps include obtaining a 163.com mail authorization code, creating a Maven

<dependency>org.springframework.boot</dependency> for spring-boot-starter-amqp and spring-boot-starter-mail

, configuring RabbitMQ and mail properties, defining a durable queue, exchange, and binding, and writing a MailUtil component that encapsulates JavaMailSender usage.

The core RabbitMQ configuration ( RabbitConfig) sets up a RabbitTemplate with confirm and return callbacks, enables manual acknowledgments, and declares the mail queue, exchange, and routing key. The producer ( TestServiceImpl) generates a unique message ID, persists a log record, and sends the message with a CorrelationData object.

The consumer ( MailConsumer) checks idempotency by querying the message log, sends the email via MailUtil.send(), updates the log status, and manually acknowledges the message. In case of failure it issues a basicNack to trigger redelivery.

A scheduled task ( ResendMsg) periodically fetches messages that remain in a pending state, increments the retry count, and re‑publishes them up to a maximum number of attempts, after which the message is marked as permanently failed.

Extensive testing sections verify exchange‑to‑exchange failures, routing failures, manual‑ack behavior, idempotency, exception handling, and the retry mechanism, with screenshots of logs, database records, and email inboxes. The article concludes with a summary of lessons learned and a link to the full source code on GitHub.