· 3 min read · Jason Youngjin Koh
Selling again to customers you have
Most brands spend almost everything on finding new customers and almost nothing on the ones who already bought. The second sale costs a fraction of the first.
Build a regular message to past customers, on Zalo in Vietnam and email in Australia, that recommends products based on what each person bought, and automate it so it runs every week without a campaign meeting. AI chooses the products, writes the copy and designs the message. The team approves and sends.
Why focus on existing customers?
The acquisition cost is already paid. A customer who bought once knows the brand and trusts the delivery. Every repeat purchase is margin a new customer ad would otherwise have spent.
A brand that sells only through ads and promotions has no relationship with its buyers. When the ads pause, sales pause with them. The customer list is the one channel the brand owns outright, and the only one that gets cheaper the longer you run it.
Should you use Zalo or email?
Use whichever your customer reads. In Vietnam that is Zalo for most people, and email is opened far less. In Australia it is email, with SMS for short and urgent messages. Brands selling in both markets usually need both.
| Zalo, Vietnam | Email, Australia | |
|---|---|---|
| How it reaches people | Official Account messages to followers, and notification templates sent to customers' phone numbers | The inbox, through an email platform |
| Best for | Short messages, product cards, order follow ups, chats that turn into sales | Newsletters, launches, collections, longer brand stories |
| Watch for | Template approval and per message costs on notifications | Consent, sender identification and unsubscribe rules |
What should each message contain?
- One reason to open: a new product, a restock, a story, a real offer. One message carries one idea.
- Products picked for the person: what pairs with their last order, what similar customers bought next, what is due for replacement.
- The brand story in small pieces, so over a few months the customer knows why the brand exists.
- One clear action.
How does AI run the program?
An agent reads the sales data and groups customers by what they bought, when, and how much they spend. For each group it picks the products most likely to sell next, writes the message in the brand's voice and produces the design. The team reviews the draft, approves and schedules. Results feed back in: which products sold from which message, which subject lines were opened, who stopped reading.
Automated flows cover the moments that matter most with nobody touching them: a thank you after the first order, a replenishment reminder when a product is likely running low, a win back message when a regular customer goes quiet.
What are the consent rules?
In Australia, the Spam Act requires consent, clear identification of the sender and a working unsubscribe in every commercial email. In Vietnam, Decree 91/2020 on spam messages, emails and calls sets similar consent and opt out obligations, and Zalo applies its own policies to what Official Accounts can send. Build consent into checkout and the program stays clean from the first message.
How do you measure it?
Revenue per message sent, and the share of total revenue that comes from returning customers. The second number shows whether the brand is building a customer base or renting one from the ad platforms every month.
Treat open rates with suspicion, particularly on email, where privacy features inflate them. Clicks and purchases are the numbers that hold up.
Retention is part of the distribution a brand builds before it runs promotions. Scale what works, test the rest