Why consent is the foundation
Every message channel depends on trust. Recipients who agreed to hear from you read, click and reply. Recipients who did not agree block, report and complain, and those complaints damage your delivery for everyone else you send to. Consent is therefore not only a legal matter but the main driver of campaign performance.
This guide sets out a practical consent programme: how to collect it, how to record it, how to honour opt-outs and how to choose sending windows. It is general guidance and not legal advice. Rules differ by country and change, so confirm the details with your own legal adviser.
What counts as good consent
- The person took a clear action, such as ticking an unticked box or sending a keyword
- They were told who you are and what you will send
- They were told roughly how often to expect messages
- They agreed for this channel, not just in general
- You can prove it later with a record
Consent that is bundled with unrelated terms, pre-ticked or inferred from a purchase is weak. It may not satisfy regulations and is much more likely to produce complaints.
Record what you need
For each contact keep the following, and keep it for as long as you may need to defend a message.
| Field | Example | Why |
|---|---|---|
| Identifier | Phone number or email | Matches the consent to the recipient |
| Channel | SMS, WhatsApp, voice | Consent is per channel |
| Date and time | 2026-10-16 10:42 IST | Proves when it was given |
| Source | Checkout form, QR code, keyword | Shows how it was given |
| Wording shown | The exact consent text at that moment | Shows what they agreed to |
| Status | Active, opted out | Controls whether you may send |
Collecting consent well
- Ask at the right moment. At sign-up, checkout or in a conversation the person started
- Be plain. Use one sentence that names your business, the channel and the type of messages
- Make it separate. Do not hide it in long terms and conditions
- Confirm it. Send a short confirmation message that repeats what they will receive and how to stop
- Store the record. Write the proof to your database at the moment of consent
Honouring opt-outs
An opt-out is the strongest signal a person can send. Treat it as final until they clearly choose to come back.
- Accept common words in any case: STOP, UNSUBSCRIBE, CANCEL, END, QUIT and local-language equivalents
- Reply once to confirm, and nothing more
- Add the number to a suppression list that every campaign checks
- Apply the suppression across all your lists and systems, not just the campaign that triggered it
- Never re-add an opted-out number from an old import
Sending windows
Even with consent, timing matters. Messages at the wrong hour feel intrusive and increase complaints. Use the recipient's local time, not yours.
| Message type | Suggested window | Reason |
|---|---|---|
| OTP and security alerts | Any time | The user is waiting |
| Order and service updates | Daytime and early evening | Useful but not urgent |
| Promotions | Late morning to early evening | Fewest complaints |
| Reminders | Evening before or morning of the event | Most actionable |
Regulators in some countries set legal windows for promotional messages and calls. Treat the legal window as the outer limit and your own, narrower, window as the working one.
Frequency and pacing
More messages do not always mean more revenue. Set a cap per person per week and apply it across campaigns, so that three teams do not each send the same person a weekly offer. Pace large sends over time rather than in one burst. Pacing protects delivery, because operators are more likely to throttle sudden spikes, and it lets you stop quickly if early results show a problem.
Auditing your programme
- Pick ten random contacts each month and trace the proof of consent for each
- Check that opted-out numbers have not been messaged
- Review complaint and block rates by campaign
- Check suppression lists are applied to every channel
- Test the opt-out keyword on each route
A sample consent and opt-out flow
Consider a retailer that collects mobile numbers at checkout. The checkout form carries an unticked box with the sentence: “Send me order updates and occasional offers on SMS and WhatsApp from Brand.” When the customer ticks it, the system stores the number, channel, time, form version and the exact sentence shown. A confirmation message goes out at once: “Brand: you will get order updates and a few offers a month. Reply STOP to opt out.”
Later, a customer replies “stop” in lower case. The inbound handler lowercases and trims every reply, recognises the keyword and marks the number opted out across SMS and WhatsApp. It sends one confirmation, “You are unsubscribed from Brand offers”, and adds the number to the suppression list that all campaigns check before sending. Nothing else is sent unless the customer opts in again through a fresh, recorded action.
Notice how little is special about this flow. The strength lies in consistency: consent is captured the same way every time, stored with proof and respected by every system.
Metrics that show consent health
| Metric | What it tells you | Action if poor |
|---|---|---|
| Opt-out rate per campaign | Whether content and frequency suit the audience | Reduce frequency, segment better |
| Complaint or report rate | Whether people feel messages were unexpected | Review consent wording and source |
| Bounce and failure rate | List quality | Clean the list and re-confirm old contacts |
| Reply rate | Engagement | Improve relevance and timing |
Compare these numbers by acquisition source. A source that produces many opt-outs, such as a purchased or partner list, is a source to stop using, whatever its volume.
Further reading
- TRAI Telecom Commercial Communications Customer Preference Regulations (India)
- Your national electronic communications and data protection laws
- Telnxo guide: WhatsApp opt-in and quality rating
Frequently asked questions
What if someone replies STOP?
Add them to your suppression list at once and do not message them again on that channel.
Is a purchase enough consent for marketing?
Usually not. A purchase can justify service messages about that purchase, but marketing generally needs its own clear consent.
How long should I keep consent records?
Keep them for as long as you might need to prove a message was permitted. Ask your legal adviser for the period that applies to you.
Do transactional messages need opt-in?
Rules differ. Many regions allow genuine transactional messages without marketing consent, but they must be truly transactional.
Can I message people who opted in years ago?
Old consent is risky. Refresh it, and remove contacts who do not engage.