Spam, Blocked Conversations, and Managing the 24-Hour Window

TL;DR

The 24-hour window (Session Window) is the basic rule of the WhatsApp Business API that affects every aspect of communicating with customers. Misunderstanding it is the cause of most “why wasn’t my message sent?” and “why was I charged for a regular message?” problems. This article covers how the window works, how to manage conversations that go unanswered, how to handle spam reports and blocks, and best practices for reducing blocks.

The 24-hour window: the basics

The WhatsApp Business API protects customers from spam through a window mechanism: a business can send a free-form message to a customer only within 24 hours of the last message the customer sent you. After 24 hours, the window closes, and you can’t send free-form messages until the customer writes again.

How the window opens

The window opens every time the customer sends you a message. It counts 24 hours from the exact time of the customer’s last message — not from midnight. If the customer sends a message at 10:00, the window is open until 10:00 tomorrow. If they send again at 15:00, the window resets and is open until 15:00 tomorrow.

How the window closes

The window closes automatically 24 hours after the customer’s last message. There’s no way to extend it manually, and there’s no warning message.

The indicator on the customer card

On the customer card in Mumble, you can see the window’s state:

• Open / green lock icon. The window is open; you can send a free-form message.
• Red lock icon. The window is closed; you can only send a message template.

The 24-hour window versus opt-in

Two separate mechanisms that new customers confuse:

The two mechanisms operate in parallel. Even if the window is open, a blacklisted customer won’t receive a message template. And even if the customer has opted in, you can’t send a free-form message after the window closes. See Opting out and the blacklist.

How to open a conversation when the window is closed

If the window is closed, there’s one way to open it: sending an approved message template. The moment the customer sees the message template and taps it or replies, the window reopens.

The procedure:

1. Check that there’s an approved message template suited to the situation.
2. Send the message template manually from the card, or through a dedicated campaign.
3. Wait for the customer to reply (it may take a while, sometimes hours).
4. Once they reply, the window is open, and you can continue with free-form messages.

Spam and blocks: how it works

WhatsApp gives customers three ways to report a business:

1. Report as spam (Report)

The customer taps “Report as spam” on the business card in WhatsApp. The report is sent to Meta and directly affects the number’s quality rating.

2. Block

The customer blocks the number. They won’t receive any further messages, and Meta is aware of the action. This too harms the quality rating.

3. Report and block together

The combination is the most negative signal to Meta. If most of the customers in a campaign both reported and blocked, the likelihood of a warning or restriction is very high.

How to recognize a spam problem

Warning signs:

• A drop in quality rating. From Green to Yellow and then to Red. See the Account Quality card in Mumble.
• A falling delivery rate. From 95% to 85% to 70%. Meta is slowing your sending.
• A message in Account Quality. “Recent quality of business-initiated messages has been low” and the like.
• A Restricted state on the account. The next step after a long drop in quality.

How to reduce the risk of blocks

• Send only to customers who gave consent. A list where you aren’t sure everyone gave an opt-in lacks consent.
• Keep a reasonable frequency. A maximum of 2–3 marketing messages per month to the same customer. More than that becomes spam in the customer’s eyes.
• Add an opt-out button to every marketing message. Use the approved word picker. See Opting out and the blacklist.
• Relevant content. Segment the audience before sending. A customer interested in certain products only should receive messages about those only.
• Don’t send without context. If the customer hasn’t received a message from you in 6 months, a sudden outreach will be seen as spam.
• Pause a campaign that shows negative signs. If the first campaign has 10% blocks, don’t send the second campaign with the same wording. Check what the customers are seeing.

Managing conversations you want to end

Sometimes you want to close a conversation on your own initiative, without harming the account’s quality. The way to do it:

A polite close

Before closing, send a final message that wraps up the inquiry and leaves the door open for a return. For example: “Thanks for reaching out! If you need any more help, we’re here. Have a great day!” Then close the conversation.

Auto-closing abandoned conversations

You can set up an automation that closes conversations that have gone unanswered for a long time. See the example in the “Auto-closing abandoned conversations” section of Automations in Mumble.

Blocking a customer on your side

If a customer is harassing you, you can block them on your side:

1. On the customer card, remove the “opt-in” so they don’t receive message templates.
2. Change the conversation status to “Blocked” or “Not relevant.”
3. If it’s a severe case, you can block the number in WhatsApp itself (in WhatsApp Manager < Phone Numbers < Block).

Common issues

I sent a free-form message and Mumble said it couldn’t be sent

The 24-hour window is closed. Send a message template instead, and wait for the customer to reply to open the window.

The customer wrote to me an hour ago and the window is still closed

Check whether the message actually arrived. Sometimes there’s a sync delay. Refresh the page. If it’s still closed after 5 minutes, contact support.

I sent a message template and the customer still doesn’t see it

Possibilities:

• The customer blocked your number in the past. Check the delivery status (delivered, read, failed).
• The customer isn’t on WhatsApp. Rare, but it happens.
• The phone number isn’t in international format. See International phone number format.

I suddenly got a lot of spam reports

Check the last campaign. It’s possible that:

• You sent to an unsuitable audience.
• The content was too aggressive, crossing a line in the customers’ eyes.
• The frequency was high (you sent 3 messages in the same week).

Pause new campaigns, clean the list, and check the rating. If the rating dropped, return to more cautious activity until it recovers. See Quality Rating: the complete guide.

I want to know whether a customer blocked me

WhatsApp doesn’t explicitly notify you of a block. An indirect sign: message templates you send will come back as failed or stay at sent without delivered. When most messages to a specific customer fail, they’ve probably blocked you.

I sent a message within 24 hours and was charged for a Marketing Conversation

This means the customer’s last message was more than 24 hours ago. Check the history. If their last message was only a few hours ago, contact Mumble support.

Related articles

• Opting out and the blacklist
• WhatsApp Quality Rating
• Bans and restrictions
• Automations in Mumble
• Message templates: the complete guide
• International phone number format

Bottom line

The 24-hour window is WhatsApp’s protection for customers, and also your protection for your business. A conversation that starts on the customer’s initiative, continues at a natural pace, and closes politely doesn’t generate spam or get accounts blocked. Respecting the 24-hour window protects your account’s quality more than any other technical setting.