How to Build Your Own Ringless Voicemail System

Looking to build a custom ringless voicemail system? This guide shows developers how to leverage Drop Cowboy to send automated voicemails at scale; without managing your own telephony infrastructure.

⚠️ Disclaimer: Ringless voicemail is regulated under the TCPA and other telemarketing laws. Always ensure compliance before sending messages.

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Overview

Ringless voicemail allows you to deliver pre-recorded audio messages directly to voicemail inboxes without ringing the recipient's phone.

Using the Drop Cowboy SDK, you can:

• Programmatically send RVM messages

• Manage number pools and caller IDs

• Track delivery results via webhooks

• Stay compliant with telecom regulations

This approach lets you build a system without provisioning your own VoIP/SIP infrastructure, while still having programmatic control over campaigns.

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Step 1: Set Up Your SDK

1. Install the Drop Cowboy SDK:

   npm install dropcowboy

2. Initialize your Drop Cowboy client using your Team ID and Secret:

   import { DropCowboy } from "dropcowboy";
   
   const dropcowboy = new DropCowboy({
       teamId: process.env.DROPCOWBOY_TEAM_ID,
       secret: process.env.DROPCOWBOY_SECRET
   });

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Step 2: Select a Private Number Pool

Each RVM message must be sent from a number in a private number pool linked to an approved brand:

const pools = await dropcowboy.listPools();
console.log(pools);

• Check service_type to make sure the pool is compatible with RVM

• Ensure number_count > 0 before sending campaigns

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Step 3: Manage Your Audio Recordings

Upload or select approved audio recordings for delivery:

const recordings = await dropcowboy.listRecordings({ api_allowed: true });
console.log(recordings);

• Supports static audio files hosted on Drop Cowboy or your servers

• Compatible with generative AI TTS messages

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Step 4: Send Ringless Voicemail Messages

Use the SDK to programmatically send messages:

const rvm = await dropcowboy.sendRvm({
    brand_id: "00000000-0000-0000-0000-000000000000", 
    recording_id: "00000000-0000-0000-0000-000000000000", 
    phone_number: "[phone]", 
    forwarding_number: "[phone]", 
    foreign_id: "YOUR_DATABASE_RECORD_ID", 
    callback_url: "https://your.server.com"
});

console.log(rvm);

• Supports advanced options like explicit caller ID campaigns

• Automatically handles delivery tracking

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Step 5: Monitor Delivery via Webhooks

Receive callbacks for each RVM delivery:

{
  "drop_id": "5c8eb7940a057a4ab0823e1a",
  "phone_number": "[phone]",
  "attempt_date": "2025-03-17T21:10:26.000Z",
  "status": "success",
  "reason": "",
  "dnc": false,
  "product_cost": 0.099,
  "compliance_fee": 0.0029,
  "tts_fee": 0.03,
  "network": {
    "name": "Verizon Wireless:6006 - SVR/2",
    "type": "wireless"
  },
  "foreign_id": "<your system value>"
}

• Track success, failures, and debug issues

• Link webhook results back to your database for campaign analytics

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Step 6: Ensure Compliance

• Only message contacts who have opted-in

• Respect TCPA and telemarketing regulations

• Log all messages and delivery results for auditing

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💡 Pro Tips

• Segment recipients for better deliverability

• Test campaigns with small numbers before scaling

• Use dynamic TTS for personalized messaging

• Monitor delivery analytics to optimize campaigns

By following this guide, developers can build their own RVM system entirely on top of Drop Cowboy’s API/SDK, without needing to maintain a separate telephony stack. Allowing clients to save time while staying compliant and scalable.