Bulk Messaging: Send SMS, MMS, and RCS to Thousands of Contacts at Once

The Difference Between Sending One Message and Sending a Million

Sending a single SMS is easy. Sending that same message to 50,000 people — reliably, quickly, at the right time, from the right number, with full delivery tracking — is a different problem entirely.

Most messaging APIs are built for transactional, one-to-one messages. They're great for sending an OTP or a shipping confirmation. But when you need to reach your entire customer base with a flash sale, a product launch, or a critical service update, you need something more: bulk messaging infrastructure.

Pinnacle ships this out of the box. Build an audience, write your message, hit send — and Pinnacle handles the distribution, load balancing, and delivery tracking automatically, across SMS, MMS, and RCS.

What Is an Audience?

Before you can blast a message, you need someone to send it to. In Pinnacle, an audience is a named list of contacts — the equivalent of a segment in email marketing.

Creating an audience is simple: give it a name, an optional description, and an initial list of contacts (phone numbers in E.164 format or existing contact IDs). If a phone number doesn't already exist as a contact in your account, Pinnacle auto-creates it — no pre-loading required.

import { PinnacleClient } from "rcs-js";
const client = new PinnacleClient({ apiKey: process.env.PINNACLE_API_KEY });
 
const audience = await client.audiences.create({
  name: "Spring Sale 2026",
  description: "Customers who opted in for promotional messages",
  contacts: ["+14155551234", "+16505559876", "+13105554321"],
});

Audiences are fully manageable: add contacts, remove contacts, rename the list, or delete it when you're done. Contacts removed from an audience aren't deleted from your account — they're just no longer in that list.

You can create and manage audiences from the dashboard, via the API, or using the Pinnacle MCP server directly in your AI-powered workflows.

Create and manage contact lists from the dashboard — no CSV imports, no third-party tools.

Sending a Blast

Once your audience is ready, sending to it takes a single API call. Pinnacle calls these blasts — a fitting name for sending one message to many people at once.

SMS Blast

The simplest blast: a text message sent to everyone in an audience.

await client.messages.blast.sms({
  audienceId: "aud_abc123",
  senders: ["+18005550001", "+18005550002"],
  message: {
    text: "🎉 Our biggest sale of the year starts NOW. Use code SPRING26 for 30% off. Reply STOP to unsubscribe.",
  },
});

MMS Blast

Add media to your blast — product images, GIFs, promotional graphics — to dramatically increase engagement.

await client.messages.blast.mms({
  audienceId: "aud_abc123",
  senders: ["+18005550001"],
  message: {
    text: "Check out what's new this spring 👇",
    mediaUrls: ["https://your-cdn.com/spring-collection.jpg"],
  },
});

RCS Blast

For recipients on supported devices, send a full rich message — branded cards, action buttons, carousels — instead of a plain text. RCS blasts go through your RCS agents instead of phone numbers.

await client.messages.blast.rcs({
  audienceId: "aud_abc123",
  senders: ["agent_your_brand"],
  message: {
    cards: [
      {
        title: "Spring Sale — 30% Off Everything",
        subtitle: "Limited time. Shop now before it's gone.",
        media: "https://your-cdn.com/spring-hero.jpg",
        buttons: [
          {
            title: "Shop Now",
            type: "openUrl",
            payload: "https://yoursite.com/sale",
          },
        ],
      },
    ],
    quickReplies: [],
  },
  fallback: {
    from: "+18005550001",
    text: "Spring Sale — 30% off everything! Shop now: yoursite.com/sale",
  },
});

For recipients whose devices don't support RCS, Pinnacle can automatically fall back to SMS — ensuring nobody gets left out. See our RCS fallback guide for details.

Every blast is logged against the audience — review past campaigns and their delivery status at a glance.

Multi-Sender Distribution

One of the subtler but most important aspects of bulk messaging is how messages are distributed across senders. Pass multiple phone numbers in the senders array, and Pinnacle automatically spreads the blast across all of them.

Why does this matter?

• Throughput: Single numbers have throughput limits. Distributing across 5-10 numbers multiplies your effective send rate.
• Deliverability: Carriers look at volume per number. Spreading load avoids triggering spam detection thresholds on any individual number.
• Redundancy: If one number has a transient issue, others continue delivering.

This is the messaging equivalent of horizontal scaling — and Pinnacle handles it transparently. You provide the senders, Pinnacle handles the routing.

Scheduling: Send at the Right Time

A flash sale message sent at 3am doesn't convert. Timing is everything in messaging, which is why Pinnacle's blast system includes full scheduling support.

One-Time Scheduled Blast

Send to your audience at a specific future time:

await client.messages.blast.sms({
  audienceId: "aud_abc123",
  senders: ["+18005550001"],
  message: {
    text: "Your flash sale starts in 1 hour. Don't miss it.",
  },
  options: {
    schedule: {
      sendAt: "2026-04-15T09:00:00Z",
      timezone: "America/Los_Angeles",
    },
  },
});

Recurring Blast

For weekly newsletters, monthly account summaries, or any repeating campaign, use a cron expression:

await client.messages.blast.sms({
  audienceId: "aud_abc123",
  senders: ["+18005550001"],
  message: {
    text: "Your weekly update from us is ready: yoursite.com/updates",
  },
  options: {
    schedule: {
      sendAt: "2026-04-07T09:00:00Z",
      recurrence: "0 9 ? * MON *", // Every Monday at 9am
      timezone: "America/New_York",
      endDate: "2026-12-31T00:00:00Z",
    },
  },
});

Recurring blasts are powerful for subscription-style messaging — weekly digests, monthly statements, appointment reminders — where you want to set up the campaign once and let it run.

Why Bulk Messaging Performs

The numbers behind SMS marketing are hard to argue with. SMS open rates average 98%, with 90% of messages read within five minutes of delivery. Compare that to email's ~20% open rate and multi-hour read lag. Businesses report generating $41 for every $1 spent on SMS marketing campaigns.

The implication: if you're running promotions, updates, or campaigns and SMS isn't in your mix, you're leaving significant engagement and revenue on the table.

And when you layer RCS on top of SMS — rich cards, interactive buttons, product carousels — those numbers climb further. Google's own case studies show brands achieving 10x higher engagement and 6x more conversions with RCS versus SMS.

The Fallback Strategy: RCS First, SMS Always

A common question: "What if my customers don't all support RCS?" The answer is the fallback message.

When you send an RCS blast, every recipient who can receive RCS gets the rich experience. Every recipient who can't — older devices, unsupported carriers — gets the SMS fallback automatically. You write both once; Pinnacle handles the routing based on each recipient's device capability.

This means you can move your entire audience to RCS-first messaging today without worrying about leaving anyone behind. The transition is automatic and invisible to your customers.

What About Building This Yourself?

Consider what you'd need to build equivalent bulk messaging infrastructure:

• Contact list management: A database of phone numbers with add/remove APIs and pagination
• Blast orchestration: Loop through contacts, call the send API for each, handle rate limits and errors
• Multi-sender distribution: Logic to round-robin or load-balance across multiple sender numbers
• Scheduling: A job queue (Celery, BullMQ, Sidekiq) with cron support and timezone handling
• Analytics: Track which blasts went to which audience, with delivery status per recipient
• RCS fallback: Device capability checking and conditional message type selection

That's a full engineering sprint — and ongoing maintenance — before you've sent a single message. Pinnacle ships all of this as a feature.

Using Bulk Messaging with the Pinnacle MCP Server

If you're building AI-powered workflows, the Pinnacle MCP server exposes bulk messaging directly to your AI agent. Create audiences, manage contacts, and trigger blasts — all via natural language:

"Create an audience called 'VIP Customers' with these 500 phone numbers, then send them an RCS message about our new loyalty program launching on April 15th at 10am Pacific."

The MCP server's create_audience, blast_sms, blast_mms, and blast_rcs tools handle all of this without a single line of manual code.

Want More Control? Build Custom Blast Logic

The API and MCP cover the common case — one message, one audience, one blast. For more sophisticated campaigns — personalized message content per recipient, A/B tested variants, dynamic audience segmentation — Pinnacle's SDK gives you full access to build the logic you need.

For enterprise bulk messaging requirements, reach out to founders@pinnacle.sh.

Frequently Asked Questions

How many contacts can an audience have?

Pinnacle doesn't impose a hard cap on audience size. Contact your account team for guidance on very large audiences (100k+).

Can I send different messages to different segments?

Yes — create multiple audiences (e.g., "West Coast Customers", "East Coast Customers") and send a tailored blast to each. Contacts can appear in multiple audiences.

What happens if a phone number in my audience is invalid or unreachable?

Invalid numbers are skipped without failing the entire blast. Delivery failures are logged and visible in the analytics dashboard — you can filter failed messages and investigate by error type.

Is there a difference between a blast and a scheduled message?

A scheduled message is a single one-to-one message sent to one recipient at a future time. A blast is a one-to-many message sent to an entire audience, with optional scheduling. Both are supported; they're just different operations.

Does the RCS blast fallback to SMS automatically?

Yes. When you include a fallback field in your RCS blast, Pinnacle automatically delivers SMS to recipients who don't support RCS — no additional logic needed on your end.

How are blasts tracked in analytics?

Every blast and its messages are visible in the analytics dashboard. Filter by sender, date range, or message type to see delivery rates, reply rates, and interaction metrics for your campaign.

Key Takeaways

• One API call, thousands of recipients: Blast SMS, MMS, or RCS to an entire audience without loops or manual orchestration
• Multi-sender distribution: Spread load across multiple numbers for higher throughput and better deliverability
• Flexible scheduling: Send immediately, at a specific future time, or on a recurring cron schedule with timezone support
• Automatic RCS fallback: Send RCS to supported devices, SMS to everyone else — Pinnacle routes automatically
• Full analytics: Every blast is tracked — delivery rates, reply rates, and interaction metrics in the dashboard
• MCP-powered AI workflows: Trigger blasts from AI agents using the Pinnacle MCP server

Get Started with Bulk Messaging

Create your first audience at app.pinnacle.sh/dashboard/audiences or via the Audiences API. For full API reference, see the blast SMS, blast MMS, and blast RCS endpoints.

If you're not yet on Pinnacle, sign up and subscribe to a plan to start sending. For questions about high-volume sending, enterprise plans, or custom integrations — get in touch.