Ringless Voicemail Drop

Send voice messages that land directly in a prospect's voicemail inbox without their phone ever ringing. This is distinct from cold calling -- the prospect discovers the message on their own time, creating a warmer callback dynamic. Pair with a same-day email referencing the voicemail for maximum impact.

Tool Options

| Tool | API Docs | Best For | |------|----------|----------| | VoiceDrop.ai | https://developers.voicedrop.ai | AI voice cloning + ringless VM in one platform, best API | | Slybroadcast | https://www.slybroadcast.com/api.php | Simple bulk delivery, lowest cost per drop | | Drop Cowboy | https://dropcowboy.com/api | Ringless VM + SMS combo, international numbers | | PhoneBurner | https://www.phoneburner.com/developer | Power dialer with VM drop on no-answer | | Kixie | https://developer.kixie.com | CRM-native VM drop, Salesforce/HubSpot integration |

Authentication

VoiceDrop.ai:

Authorization: Bearer {VOICEDROP_API_KEY}
Base URL: https://api.voicedrop.ai/v1

Slybroadcast:

Base URL: https://api.slybroadcast.com/v1
c_uid: {SLYBROADCAST_UID}
c_password: {SLYBROADCAST_PASSWORD}

Operations

1. Upload a pre-recorded voicemail

If using audio generated by the ai-voice-generation fundamental, upload it first.

VoiceDrop.ai:

POST https://api.voicedrop.ai/v1/voicemails
Content-Type: multipart/form-data

file: @vm-sarah-acme.mp3
name: "sarah-acme-outbound-mar24"

Response includes voicemail_id.

Slybroadcast:

POST https://api.slybroadcast.com/v1/audiofiles
Content-Type: multipart/form-data

c_uid: {UID}
c_password: {PASSWORD}
audio_file: @vm-sarah-acme.mp3

2. Send a ringless voicemail to a single number

VoiceDrop.ai:

POST https://api.voicedrop.ai/v1/drops
{
  "voicemail_id": "{VOICEMAIL_ID}",
  "phone_number": "+14155551234",
  "caller_id": "+14155559876",
  "metadata": {
    "prospect_id": "abc123",
    "campaign": "outbound-voice-messages",
    "prospect_name": "Sarah Chen"
  }
}

Slybroadcast:

POST https://api.slybroadcast.com/v1/campaigns
{
  "c_uid": "{UID}",
  "c_password": "{PASSWORD}",
  "c_callerID": "+14155559876",
  "c_phone": "+14155551234",
  "c_audio": "{AUDIO_FILE_ID}",
  "c_date": "now",
  "c_time": "now"
}

3. Batch-send ringless voicemails

For sending personalized voicemails to a list, iterate over prospects:

VoiceDrop.ai batch:

POST https://api.voicedrop.ai/v1/campaigns
{
  "name": "outbound-voice-mar24-batch1",
  "drops": [
    {
      "voicemail_id": "{VM_ID_1}",
      "phone_number": "+14155551234",
      "caller_id": "+14155559876",
      "scheduled_at": "2024-03-15T10:00:00-05:00"
    },
    {
      "voicemail_id": "{VM_ID_2}",
      "phone_number": "+14155555678",
      "caller_id": "+14155559876",
      "scheduled_at": "2024-03-15T10:05:00-05:00"
    }
  ],
  "metadata": {
    "campaign": "outbound-voice-messages",
    "level": "baseline"
  }
}

Schedule drops during business hours (9am-11am local time) for highest callback rates.

4. Check delivery status

VoiceDrop.ai:

GET https://api.voicedrop.ai/v1/drops/{DROP_ID}

Returns: status (delivered, failed, pending), duration_seconds, cost_units, delivered_at.

Possible statuses:

• delivered -- voicemail successfully deposited
• failed_carrier -- carrier blocked the drop
• failed_invalid -- number disconnected or invalid
• failed_landline -- some carriers block ringless VM on landlines

5. Get campaign analytics

VoiceDrop.ai:

GET https://api.voicedrop.ai/v1/campaigns/{CAMPAIGN_ID}/stats

Returns: total_drops, delivered, failed, delivery_rate, callback_count (if tracking number used), cost_units_consumed.

Delivery Best Practices

• Timing: Send between 9am-11am in the prospect's local timezone. Tuesday-Thursday delivers highest callback rates.
• Caller ID: Use a local area code matching the prospect's region. This increases callback rate by 2-3x.
• Length: Keep messages under 30 seconds. Voicemails over 45 seconds get deleted before finishing.
• Follow-up: Send an email within 1 hour of the voicemail drop referencing it: "I just left you a quick voicemail about..."
• Frequency: Maximum 1 voicemail per prospect per week. 2 ringless VMs in a campaign (Day 1 and Day 7) is the sweet spot.

Error Handling

• Carrier blocks: Some mobile carriers reject ringless VM. Delivery rates typically range 70-85%. Do not retry failed drops on the same number -- the carrier will continue blocking.
• DNC compliance: Check numbers against the National Do Not Call Registry before dropping. VoiceDrop.ai includes built-in DNC scrubbing. Slybroadcast requires you to scrub first.
• Wrong timezone: If you don't know the prospect's timezone, use Clay enrichment to detect it from their location. Dropping a voicemail at 6am is worse than not sending one.
• Cost overruns: VoiceDrop.ai charges per "voice unit" (~150 chars). A 30-second message uses 2-3 units. Monitor usage via the subscription API endpoint.

Pricing

| Tool | Plan | Cost | Included | |------|------|------|----------| | VoiceDrop.ai | Starter | $95/mo | ~1,000 ringless VMs | | VoiceDrop.ai | Growth | $495/mo | ~6,500 units (~2,500 VMs) | | Slybroadcast | Pay-as-you-go | $0.04/drop | No minimum | | Drop Cowboy | Starter | $7.50/mo + $0.05/drop | Pay per use | | PhoneBurner | Standard | $140/user/mo | Unlimited VM drops (requires dialer) | | Kixie | Professional | $65/user/mo | VM drop included with dialer |