If your website, online store or software needs to send email automatically, you have two main options: connect to an SMTP relay, or call an email API. Both deliver the same email in the end. The right choice depends on what your platform supports, what your developers prefer and how much data you want back. Mailpro offers both, on the same Swiss-hosted infrastructure.
The short version
| SMTP relay | Email API | |
|---|---|---|
| Setup | Enter server, port, username and password | Write code to call HTTP endpoints |
| Best for | Existing software with an SMTP setting | New integrations and custom apps |
| Data back | Delivery logs and statistics | Structured responses, webhooks, detailed events |
| Contact management | Sending only | Sending plus list and contact actions |
| Developer effort | Minimal | Moderate |
When SMTP is the practical choice
Many platforms popular with Australian small businesses, such as accounting packages, booking systems, WordPress sites and point-of-sale tools, offer an SMTP setting and nothing more. In that case, point them at Mailpro’s SMTP server and you’re done: invoices and booking confirmations go through a managed relay rather than your own mailbox, with better deliverability and a log of every message. Our FAQ on the difference between SMTP and API covers the technical detail.
When the API is worth the extra work
If you’re building a SaaS product, a custom online store or a mobile app, the API gives you more control. You can send templated messages with variables, add and update contacts, handle unsubscribes programmatically and receive delivery events in real time through webhooks. That’s useful when, for example, an Australian retailer wants a “your parcel is out for delivery” email to update its customer portal as soon as the message bounces.
Compliance is the same either way
The Spam Act 2003 doesn’t care how a message was sent. If an email sent through SMTP or the API promotes goods, services or your business, it’s a commercial electronic message and needs consent, sender identification and a working unsubscribe that is actioned within five working days. Pure transactional messages, such as receipts, are generally outside the Act’s consent requirement. The risk is the grey zone: a receipt with a “shop our new range” banner is now commercial.
Under the Privacy Act 1988, both routes involve disclosing personal information to your email provider. If that provider stores data overseas, APP 8 applies. Mailpro stores all data in Switzerland on private infrastructure, outside US jurisdiction, for both SMTP and API traffic.
Security
- Both routes use encrypted connections, with TLS 1.3 supported.
- For SMTP, use authenticated connections on port 587 or 465, never an open relay. See SMTP authentication.
- For the API, keep keys out of source code and rotate them if a developer leaves.
- Authenticate your sending domain with SPF, DKIM and DMARC whichever route you choose.
A decision guide by business type
- Sole trader or small office sending invoices from an accounting package: SMTP. There is nothing to code, and the relay log answers “did the client get the invoice?”
- WordPress or WooCommerce store: SMTP through a mail plugin is usually enough. Move to the API if you build custom order flows.
- Booking platform or SaaS product built in-house: API. You will want webhooks to update booking status automatically when a confirmation bounces.
- Multi-site retailer with a central ERP: often both, SMTP for legacy systems and the API for the customer-facing app.
- Agency managing several Australian clients: the API makes it easier to separate clients, templates and reporting programmatically.
Performance and reliability
For most Australian businesses, speed is not the deciding factor: both routes hand messages over in seconds. What matters more is how failures are handled. With SMTP, your software usually learns only that the message was accepted; bounces show up later in the Mailpro log. With the API, your code gets a structured response and can receive bounce and delivery events through webhooks, so your app can flag a wrong address to the customer while they are still on the checkout page. If your support team spends time on “I never got the confirmation” calls, that feedback loop is worth the extra development.
Plan for peaks either way. EOFY in June and the Black Friday to Christmas stretch bring the highest transactional volumes for many Australian retailers, and a queue that works in March may not in late November. Test your integration with realistic volumes before the season starts.
Can you use both?
Yes. A common Australian setup is SMTP for the accounting system’s invoices, and the API for the online store’s order flow, with both reporting into one Mailpro account. Our article on SMTP relay versus email API shows more combinations.
Whatever you choose, pricing is based on the number of emails sent, and you can start with 500 free credits.