Modernising Legacy SMTP Payload Systems in Government

sath65
Aug 31
2 min read

The Challenge

In Canberra, many legacy government systems still rely on payload over SMTP for delivering transactional data. These systems often generate tens of thousands of email transactions per day, pushing the boundaries of what traditional infrastructure can handle.

As departments transition to Microsoft 365 (M365), new challenges arise:

Daily send limits in Exchange Online make it difficult for legacy batch systems to sustain their volume of outbound traffic.
Compliance and throttling rules can interrupt critical data flows.
Retrofitting these systems to modern APIs often requires extensive redevelopment.

This creates a situation where business-critical legacy applications struggle to remain viable within the M365 environment.

Interim Solution – Amazon SES

For departments that cannot immediately modernise their legacy applications, Amazon Simple Email Service (SES)offers a practical and cost-effective bridge:

Scales easily to handle high-volume SMTP transactions.
Low operating cost, well suited for budget-sensitive government environments.
Provides transactional reliability, ensuring payloads continue to flow as expected.

SES allows agencies to keep legacy SMTP-based applications running while transitioning to cloud-first strategies.

Long-Term Direction – REST-Based Services

While SES provides short-term relief, relying indefinitely on SMTP payloads is not sustainable. For long-term resilience and efficiency, REST-based services are the recommended path:

Greater scalability with modern APIs.
Richer data contracts and payload flexibility compared to SMTP headers and attachments.
Improved monitoring and observability, with clearer error handling.
Better alignment with modern cloud architectures and zero-trust principles.

Departments should plan a progressive migration of these transactional workloads from SMTP to REST services, reducing technical debt and improving interoperability with cloud platforms.

Conclusion

Short term: Leverage Amazon SES to support high-volume SMTP transactional systems as agencies migrate to M365.
Long term: Invest in REST-based service integrations to modernise payload delivery, improve scalability, and reduce reliance on email infrastructure.

At Azooa, we help agencies design pragmatic transition pathways — balancing today’s operational demands with tomorrow’s modern, secure cloud architectures.