Every company that sells via WhatsApp eventually thinks about notifying their entire contact base about a promotion. Half never do it out of fear of being blocked; the other half do it wrong and learn to fear it afterward. Both issues can be solved by understanding what really causes a number to be blocked — and it’s not the volume of messages.
In this article
- Broadcast, mass messaging, and campaigns: three different things
- Why a number gets blocked
- The rules you need to follow
- Preparing the list before the message
- The account that changes the outcome
- How to write the message
- What to measure after each campaign
- Mistakes that get your number blocked
- Frequently Asked Questions
Broadcast, mass messaging, and campaigns: three different things
Most problems with mass sending start from confusion over terminology. It’s worth clarifying before anything else.
Broadcast list is a feature of the app itself: you create a list and the message is delivered individually to each person. It has a crucial and little-known limitation — only those who have your number saved in their contacts receive it. In practice, this is why companies send to 800 contacts but only get responses from thirty.
System mass messaging is sending done through a tool connected to your number, without relying on the recipient’s contacts. It solves reach but creates another responsibility: now you define the pace, list, and content — and you are accountable for the consequences.
Segmented campaign is mass messaging done with criteria: a specific segment of the base, with a message written for that segment. It’s the only one of the three that usually justifies the effort, and the rest of this article focuses on it.
Why a number gets blocked
WhatsApp does not block for "sending too many messages." It blocks based on signals that people did not want to receive those messages. The main reasons are four:
Reports and blocks by recipients. By far the strongest factor. When many people mark your message as spam or block the number in succession, the system gets the message. A cold list produces this pattern in minutes.
Volume inconsistent with the number’s history. A number that exchanges fifty messages a day and suddenly sends a thousand, all initiated by it, without any replies, shows easily identifiable behavior.
New number acting like an old number. A SIM card bought yesterday that sends to a thousand people today is the most predictable case of blocking.
Problematic content. Exaggerated promises, restricted product offers, suspicious shortened links, or identical text sent thousands of times.
The point that sums it all up: the risk is not in the number of messages, but in the proportion of people who did not want to receive them. A thousand messages to customers who purchased in the last quarter are safer than a hundred to a purchased list.
The rules you need to follow
There are three layers of rules, and they are not optional.
Consent (and LGPD). In Brazil, processing personal data for commercial communication requires a legal basis. In everyday commercial practice, this means: sending to those who contacted your company, bought something, filled out a form, authorized in registration — and never to purchased or scraped social media lists. Besides being a legal requirement, this is what separates campaigns that convert from those that get your number blocked. Keep a record of where and when each contact gave authorization.
Easy opt-out. Every campaign needs a clear way to opt out: "reply STOP to unsubscribe." And the request must be respected immediately, with the contact marked in the system. Those who reply STOP and receive messages again the following week report it — and reports are what get numbers blocked.
Official API rules, if you use that route. On Meta’s API, messages initiated by the company must use a pre-approved template, and there is a 24-hour window: after the customer replies, the conversation flows freely during this period; outside it, only templates can be used. There is a charge per conversation, which varies by category and is periodically reviewed — check Meta’s current table before budgeting. This is detailed in the article about the Official WhatsApp Business API.
Prepare the list before preparing the message
A good campaign is 70% list and 30% text. Before writing anything:
- Clean the list. Remove invalid numbers, duplicates, and those who have already opted out. Sending to nonexistent numbers is a bad sign and a waste.
- Confirm who really has WhatsApp. Many old lists include landlines and deactivated cell phones.
- Segment by engagement. Those who purchased in the last 90 days, those who replied to any message in the last year, those who only registered and never interacted. These are three different audiences and should not receive the same message.
- Start with the warmest contacts. An initial send to those with recent company interaction generates replies — and replies are the best reputation signal your number can accumulate.
If the number is new or has never been used for sending, go slow in the first weeks: small volume, gradually increasing, always prioritizing those who reply. A number that converses before announcing builds history — and history supports larger campaigns later on.
The account that changes the outcome
A base of 2,400 contacts accumulated over three years. Two ways to use the same base:
Scenario A — mass messaging everyone. 2,400 identical messages with a generic promotion. Response rate of 3%: 72 conversations. Of these, 11 became sales, with an average ticket of R$ 290: R$ 3,190. On the other side: dozens of blocks, a handful of reports, and a number with compromised reputation for the rest of the year.
Scenario B — three segmented campaigns. 420 contacts who purchased in the last 90 days receive a repurchase offer for a complementary product; 260 who replied but did not buy receive a follow-up with a first-purchase incentive; 180 inactive for over a year receive a short reactivation message. Total: 860 messages, with an average response rate of 19%: 163 conversations. Of these, 17 became sales: R$ 4,930.
Scenario B sent 64% fewer messages, earned 55% more revenue, and did not put the number at risk. It’s not luck: a message written for a specific situation always converts better than a message written for everyone — and those who receive something relevant do not report it.
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How to write the message
Four parts, in this order, with the entire text fitting in five lines:
- Immediate identification. Who is speaking, right in the first line. No one reads a message from an unknown number that starts with "Hi, how are you?".
- Reason for contact related to the person. "You last changed your filter in March" is infinitely better than "we have news."
- A concrete offer, with a deadline. Without a deadline, the message becomes a reminder that no one acts on. Too long a deadline also has the same effect.
- A question that invites a short reply. "Would you like me to reserve it?" generates conversation; "visit our website" generates silence. And replies protect the number’s reputation.
Vary the text among recipients — even if it’s just the first name and one intermediate sentence. Absolutely identical messages sent thousands of times are an easy pattern to identify, besides sounding like a circular.
What to measure after each campaign
- Delivery rate: how many were actually sent. A drop here indicates a dirty list or a number with issues.
- Response rate: the most important indicator. Below 5% on your own base means a cold list or wrong message.
- Opt-out and block rate: the brake. If it exceeds 2%, stop and review segmentation before the next send.
- Conversations that turned into sales and revenue per thousand messages sent — this number allows comparing campaigns.
Record these four numbers for each campaign in the same spreadsheet. In three months you’ll have a clear picture of which segment responds, which offer works, and which message wastes reputation without return. It’s the same logic as customer service metrics: without records, each campaign starts from scratch.
Mistakes that get your number blocked
- Buying lists. Illegal from a data protection standpoint, ineffective commercially, and the fastest path to being blocked.
- Sending everything at once on the first day. High and sudden volume on a number without conversation history is the classic spam pattern.
- Ignoring opt-out requests. It costs one click to respect and the entire number to ignore.
- Using the company’s main number for testing. If you want to experiment with volume, use a secondary number until you understand your base’s behavior.
- Sending promotions to those who just bought the same product. Besides annoying, it signals poor base organization.
- Not having anyone to respond. A campaign that generates 163 conversations and finds two busy agents wastes the lead’s best moment — which is why mass messaging without customer service structure usually yields less than expected.
The safe path
Start small and with those who already like you: separate contacts who purchased in the last ninety days, write a message specific to that situation, send with easy opt-out, and monitor replies, opt-outs, and sales. If the numbers look good, expand to the next segment the following week.
Mass messaging is neither forbidden nor unethical — what breaks companies is mass messaging without criteria. The difference between a campaign that generates revenue and one that gets the company’s number blocked is not the tool or volume: it’s sending to those who have a reason to receive it, with a message that person recognizes as directed to them.
Frequently Asked Questions
Is mass messaging on WhatsApp allowed?
Sending commercial messages to contacts who authorized contact is a legitimate and common practice. What is not allowed — neither by platform rules nor data protection laws — is sending to purchased lists, to those who never had a relationship with the company, or to those who have already opted out. Keep records of where and when each contact authorized and always offer a simple way to unsubscribe.
Why was my number blocked after a mass message?
Almost always due to reports and blocks by recipients in succession, not the volume itself. Cold lists, generic messages, newly created numbers sending high volume, and identical text to thousands are the four main risk factors. A thousand messages to recent customers are usually safer than a hundred to a purchased list.
What is the difference between a broadcast list and system mass messaging?
In the app’s broadcast list, only those who have your number saved in their contacts receive it — so the real reach is usually a fraction of the list. System mass messaging does not depend on the recipient’s contacts and allows segmentation, personalization, and measurement of results, but transfers responsibility for pace, content, and list quality to the company.
How many messages can I send per day without risk?
There is no magic number because what matters is the proportion of people who did not want to receive the messages. A number with conversation history, sending to its own recent base, supports much higher volumes than a new number sending to an old list. The safe practice is to grow gradually, prioritize the warmest contacts in the first sends, and slow down whenever the opt-out rate exceeds 2%.
What response rate should I expect in a campaign?
On a well-segmented own base, response rates of 15% to 20% are achievable. In generic sends to the entire base, it’s common to see around 3%. This difference explains why smaller, segmented campaigns usually generate more revenue than broad sends — with a fraction of the messages and without risking the number’s reputation.
Segmented campaign, with replies on the other side
VeyloCRM segments your base by behavior, sends with pace and opt-out control, and routes every reply to the team’s service queue — no improvisation.