Customer communication: email, SMS, WhatsApp and chat in one flow

Start from the customer record, not from the channels. Most businesses add email, SMS, WhatsApp and chat one tool at a time, and each tool keeps its own contacts, consent and history. The fix is one record per customer that stores language, preferred channel and consent per channel, and one set of rules that decides which event triggers which message. The channels then become interchangeable outputs. You can keep your current providers in most cases; what changes is who decides and where the data lives.

Which channel fits which message?

Each channel has its own cost, reach and rules. Email is cheap and carries documents but competes with spam filters. SMS reaches any phone and suits short, urgent messages, at a per-message price. WhatsApp is best for two-way service with customers who opted in. A chatbot answers questions before anyone needs to call. Match the channel to the message, not to habit.

Channel	Good for	Marketing consent	Cost pattern	Watch out for
Email	Receipts, documents, newsletters	Needed, with an existing-customer exception	Low per message	Authentication and spam placement
SMS	Reminders, delivery windows, codes	Same rule as email	Per message; longer texts are billed as several	Short format, no rich content
WhatsApp Business API	Two-way service, notifications	Needed, and Meta requires an opt-in	Per template message, set by Meta	Templates need Meta approval
Website chatbot	Pre-sale questions, status, routing	Not needed; the visitor starts it	Hosting and AI usage	Must hand over to a person

How is the system put together?

Events come from the systems where things happen: the shop sends “order paid”, the booking tool sends “appointment tomorrow”, the ERP sends “delivery scheduled”. A rules layer reads the customer record, checks consent for marketing messages, picks the channel and language, and sends through the provider’s API. Delivery status, replies and opt-outs come back through webhooks and are written to the same record.

Two design decisions matter most. First, a single suppression list: in the outreach platforms we built for a SaaS client, an opt-out or bounce recorded by one instance is honored by all of them (startup discovery and outreach platform). Second, sending hygiene: authenticated domains and delivery monitoring. We built 15 free deliverability tools, including SPF, DKIM and DMARC checkers, for InboxRatio, and PingMyUsers compares email, SMS, OTP and WhatsApp APIs with a source for every fact, so we choose providers on documented evidence.

Example: a car garage with two locations near Lucerne

Illustrative scenario, not a client project.

A garage with two workshops and a small sales team books services by phone and email. Customers get no confirmation, reminders go out on paper, and the tire-change season in spring and autumn floods the phone lines.

After the project, an online booking creates an email confirmation and an SMS reminder the day before. When the car is ready, the customer gets a WhatsApp message if they opted in, an SMS if not. A website chatbot answers opening hours, prices for standard services and “is my car ready?” from the workshop system. Before each tire season, customers with marketing consent, or covered by the existing-customer exception, receive an email with a booking link. Everything they reply, in any channel, lands on their record.

What rules apply to email, SMS and WhatsApp?

In Switzerland, under the Unfair Competition Act (UCA Art. 3 para. 1 let. o), mass advertising by email, SMS or similar channels requires prior consent, a correct sender identity and a free, easy opt-out. Existing customers may receive advertising for similar products if they were given the chance to refuse. Order confirmations and booking reminders are generally treated as service messages rather than advertising, as long as you keep promotions out of them.

Online shops must also confirm orders electronically without delay (UCA Art. 3 para. 1 let. s). The revised FADP requires your privacy notice to name the recipients, or categories of recipients, of customer data and, where providers store it abroad, the countries involved. The FDPIC’s advertising page summarizes the consent rules. For recipients in the EU, the GDPR and national e-privacy rules set comparable requirements.

How does a project run?

1. Discovery. We list every message you send today, from which tool, to whom, with which consent basis.
2. Architecture. Customer data model, consent storage, event list, channel rules and provider choice.
3. Build. Templates in each language, integrations and chatbot, tested on staging with test numbers and addresses.
4. Launch. Service messages first, marketing flows once consent data is clean.
5. Iterate. Delivery, reply and opt-out rates reviewed per message type; messages that nobody needs are removed.

You receive a fixed-price or phased proposal after discovery. For online shops, the order-side flows are covered in e-commerce automation.