Email inboxes are overloaded and promotionally polluted. SMS cuts through because it feels different. Here's how to use it properly for transactional messages.
Business owners and developers who send transactional messages to customers — confirmations, alerts, payment receipts, job updates — and want those messages to actually be seen.
Should we be using SMS instead of email for transactional messages, and how do we do it properly?
Think about your own inbox. Right now. How many unread emails are sitting there? For most people, it's dozens — sometimes hundreds. Promotions, newsletters, platform updates, SaaS notifications, sale announcements. It's all mixed together.
Your invoice confirmation landed in that same inbox. So did the appointment reminder, the job completion notice, and the payment receipt. They're buried.
The average office worker receives around 120 emails a day. The average open rate for business email sits around 20%. That means 4 out of every 5 emails go unread — and the ones that do get opened are often checked hours or days later.
There are three specific reasons email has broken down as a transactional channel:
Promotions poisoned the inbox. Email marketing became so cheap and so accessible that everyone used it for everything. The result is an inbox that looks like a shopping centre letterbox. Customers learned to skim and delete by habit.
Spam filters are aggressive. Even well-formatted, legitimate transactional emails end up in spam regularly. A shared sending domain, a poorly formatted header, a new sending IP — any of these can route your payment confirmation straight to junk. The customer never sees it. You never know.
There is no visual distinction between important and promotional. An invoice notification and a discount code look identical in a list view. Subject lines are scanned in under a second. If yours doesn't hit immediately, it's gone.
The core problem: Email works fine as a communication channel. It fails when you need something seen quickly and reliably. That is exactly what transactional messages require.
SMS has a 98% open rate. Not because SMS is magic — because it's still rare enough that a message on your phone means something. People check SMS immediately, almost without thinking. It interrupts. That is the entire point.
When someone gets an SMS, their default assumption is that it matters. It's from a real person, a bank, a delivery driver, a doctor's clinic. That assumption is earned because SMS hasn't been abused the way email has.
SMS is also harder to fake credibility with. Spam emails can look polished and professional. A spam SMS looks like a spam SMS — badly written, suspicious link, generic sender. Customers have developed a reasonable filter: if it's SMS and it looks like a business they deal with, they'll read it.
Speed matters too. The average SMS is read within 3 minutes of delivery. For time-sensitive messages — a technician is 10 minutes away, your payment failed, your booking is confirmed — this is the difference between a good customer experience and a frustrated phone call to your office.
This is where most businesses destroy the value of SMS.
The moment a customer gets a discount code via SMS from the same number that sends their appointment reminders, the trust is gone. That number is now a marketing channel. They'll start ignoring it, or worse, block it. Your payment confirmations stop getting seen.
Transactional SMS works because customers know what to expect from it. It's a signal, not a channel. The signal is: something happened with your account, your order, your job, your booking. That signal only has value if it's never diluted.
If your marketing team asks to add a promotion to the bottom of your transactional SMS — say no. "Your invoice is ready. P.S. 20% off this weekend" is the fastest way to turn a trusted notification channel into ignored noise.
Businesses often have a legitimate reason to use SMS for both transactional messages and marketing. That's fine — but they need to be separated completely.
Use a dedicated number (or short code) for transactional messages only. Use a different number for marketing. Make sure the sender ID is clearly different so customers can see immediately which is which.
When customers opt in to receive marketing SMS, they're saying yes to that number, not to everything you might ever send. Keeping them separate also helps with compliance — transactional messages operate under different rules than marketing messages (more on that below).
| Message type | Examples | Number to use |
|---|---|---|
| Transactional | Invoice ready, job complete, appointment reminder, payment received, order shipped | Dedicated transactional number |
| Promotional | Sale announcement, new product, discount code, loyalty offer | Separate marketing number |
Here are the most common use cases we build into client systems — all of these are triggered automatically based on something happening in the business software, not manually sent by staff.
Systems like SimPRO, Tradify, and ServiceM8 manage jobs for trades businesses. When integrated with an SMS gateway, you can automatically send:
When your accounting system (Xero, MYOB) raises an invoice or records a payment, an SMS can go out automatically:
For healthcare, professional services, or any appointment-based business:
For WooCommerce, Shopify or custom order systems:
For internal business processes where someone needs to approve a step:
For monitoring, access, and authentication:
If you have a custom web app, a job management system, or any software that triggers events — adding SMS is usually straightforward. It's a single API call to an SMS gateway when the event occurs.
The main providers used in Australia:
The typical integration pattern is simple:
If you're using an off-the-shelf system like SimPRO or Xero that doesn't natively trigger SMS, the integration typically sits in middleware — a small connector that listens for events via webhook or polling and fires the SMS on your behalf.
Cost is not a barrier. SMS via Twilio or ClickSend costs between 6 and 12 cents per message in Australia depending on volume. For most businesses, SMS costs are negligible compared to the staff time saved on follow-up calls and the improvement in customer experience.
Australia's Spam Act 2003 and the ACMA rules apply to SMS. The key points:
Transactional messages do not require prior consent — if a customer gave you their mobile number in the context of a transaction (booking, purchase, job), sending them a message directly related to that transaction is covered. You don't need an explicit opt-in for "your job is complete" or "your payment was received."
Marketing messages always require consent. If you're using SMS to promote products or services to existing or prospective customers, you need an explicit opt-in. No exceptions.
Always provide a way to opt out. Even for transactional messages, best practice is to include a simple opt-out method — "Reply STOP to unsubscribe from these notifications." This keeps you on the right side of customer expectations and the law.
Sender ID. You can register an alphanumeric sender ID (e.g. "HelloPeople" instead of a phone number) with most Australian providers. This improves trust and brand recognition. Note that customers cannot reply to alphanumeric sender IDs — if you need two-way messaging (replies to confirm bookings, etc.), use a dedicated number instead.
If you're unsure about compliance for your specific use case, the ACMA website has clear guidance, or talk to your legal advisor before launching.
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