When a company decides to run a mass campaign, the first question tends to be operational: send it by email or by WhatsApp?

That's not the best question.

The right question is: which conversation does this campaign need to start?

Email and WhatsApp have different strengths. Email is good for longer content, offers that need more explanation, newsletters, recurring communications, rich materials, base relationship-building, and campaigns that don't require an immediate reply. It's cheaper to scale, easier to organize into lists, and historically strong for nurturing.

WhatsApp is different. It's more direct, more intimate, and more sensitive. The customer perceives the message as a conversation, not as a piece of media. That can increase attention and response, but it also increases the risk of annoyance when the message lacks context.

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That's why a WhatsApp campaign can't be treated as a generic blast. On WhatsApp, messages started by the company usually depend on templates, category, and Meta's rules. The channel allows campaigns, promotions, and re-engagement, but it demands more care with consent, frequency, and relevance.

Email tolerates volume better. WhatsApp demands more intent.

Recent data from Opinion Box helps explain why this choice needs to be made with judgment: 82% of Brazilians say they communicate with brands through WhatsApp, and 60% consider it appropriate to buy products or services through the channel. That shows commercial strength, but it also raises the responsibility. When a company enters a customer's WhatsApp, it enters a conversation space, not an impersonal storefront.

In practice, email tends to work better when the company wants to educate, explain, nurture, or communicate to a broad base. WhatsApp tends to make more sense when there's urgency, high intent, a prior relationship, or a need for a quick reply.

An e-commerce business can use email to present a collection, tell a brand story, nurture customers, and work recurring offers. It can use WhatsApp for a more specific opportunity: a customer who asked for information, abandoned an important step, opted in to receive offers, or needs consultative service.

A clinic can use email for guidance content, news, and institutional campaigns. It can use WhatsApp for confirmation, rescheduling, reminders, and clear guidance before an appointment.

A B2B company can use email to educate leads, send materials, and maintain a relationship. It can use WhatsApp to advance conversations with people who have already shown interest, asked for contact, or are in negotiation.

The most common mistake is trying to fix a lack of strategy by increasing volume. When email underperforms, the company rushes to WhatsApp. When WhatsApp generates blocks or low response, it blames the channel. But the problem is often upstream: a disorganized base, a generic message, a weak offer, and no metrics.

A mature campaign needs to answer five questions before it goes out:

  • who is the message for;
  • why should this person receive it now;
  • what action are we expecting;
  • how will we measure the result;
  • what happens after the reply.

That last point is decisive. On WhatsApp, a reply is not a sale yet. If the campaign generates conversations and the team has no process to attend, qualify, route, and log them, the company trades silence for chaos.

There's also an important expectation gap. With email, the customer accepts replying later. On WhatsApp, they expect continuity. If the company invites the customer to talk, it needs to be ready to respond.

This is where email and WhatsApp can work together. Email can open the relationship, educate, and segment interest. WhatsApp can accelerate warmer conversations, confirm intent, and move the customer to the next step. The CRM needs to connect both so the company doesn't treat each channel as a separate world.

This is where Merge comes in: helping companies turn campaigns into a commercial operation. It's not enough to choose the channel that gets the most attention. You need to know when to use each channel, how to log consent, how to measure return, and how to turn a reply into a sale, service, or relationship.

The best channel isn't the one that delivers the most messages. It's the one that starts the right next conversation with the right person.

Practical action for businesses

  • Use email for nurturing, content, broad campaigns, and less urgent communications.
  • Use WhatsApp for contacts with more intent, urgency, a prior relationship, or a need for a quick reply.
  • Don't send a WhatsApp campaign without consent, a goal, segmentation, and a service plan.
  • Measure open rate, clicks, replies, opt-outs, opportunities, and sales by channel.
  • Integrate campaigns with the CRM so a reply becomes a next step, not a lost conversation.