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Overview

Transmit provides a unified platform for sending communications across multiple channels. Whether you need to send transactional emails, SMS notifications, or voice calls, you can do it all through a single API with consistent patterns and behaviors.

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Why Multi-Channel?

Modern applications need to reach users where they are. Different use cases call for different channels:

Email

Rich content, receipts, newsletters, detailed notifications

SMS

Time-sensitive alerts, 2FA codes, delivery updates, urgent notifications

Voice

Critical alerts, two-factor authentication, appointment reminders

Unified Analytics

Track engagement across all channels in one dashboard

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Email Channel

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Capabilities

Email is perfect for rich, detailed communications:
  • Rich HTML content with images, styling, and layouts
  • Attachments for documents, invoices, and files
  • Templates for consistent branding
  • Personalization with dynamic content
  • Tracking for opens, clicks, and engagement
  • Bulk sending for newsletters and campaigns

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Quick Example

const response = await client.emails.send({
  from: 'notifications@yourdomain.com',
  to: 'user@example.com',
  subject: 'Order Confirmation #1234',
  html: `
    <h1>Thank you for your order!</h1>
    <p>Your order #1234 has been confirmed.</p>
    <a href="https://yourdomain.com/orders/1234">View Order</a>
  `,
  tracking: {
    opens: true,
    clicks: true
  }
});

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Best Practices

Always verify your sending domain with SPF, DKIM, and DMARC records to improve deliverability and build sender reputation.
Include plain text versions of your emails for recipients who can’t view HTML or prefer text-only emails.
Track open and click rates to optimize your email content and sending patterns.
Monitor bounce events and remove hard-bounced addresses from your lists to maintain sender reputation.

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SMS Channel

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Capabilities

SMS is ideal for time-sensitive, high-priority communications:
  • High open rates (98% within minutes)
  • Two-factor authentication codes
  • Delivery notifications and order updates
  • Appointment reminders
  • Global reach with international numbers
  • Unicode support for emojis and special characters
  • Delivery receipts for confirmation

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Quick Example

const response = await client.sms.send({
  from: '+1234567890',
  to: '+1987654321',
  body: 'Your verification code is 123456. Valid for 10 minutes.'
});

console.log('SMS sent:', response.id);
console.log('Status:', response.status);

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SMS Features

Character Limits & Segmentation
  • Standard messages: 160 characters per segment
  • Unicode messages: 70 characters per segment
  • Automatically segments longer messages
  • Track segment count for billing transparency
Opt-In/Opt-Out Management
  • Built-in subscription management
  • Automatic handling of STOP/START keywords
  • Compliance with TCPA and carrier regulations
  • Consent tracking and audit logs
US Compliance (A2P 10DLC)
  • Automatic brand and campaign registration
  • Improved deliverability on US carriers
  • Reduced filtering and blocking
  • Transparent registration status

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Best Practices

Keep messages short and actionable. SMS is for urgent, important information only.
Send messages during appropriate hours (9 AM - 8 PM local time). Respect time zones.
Use a recognizable sender ID or short code so recipients know who’s messaging them.

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Voice Channel

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Capabilities

Voice calls provide the highest level of urgency and attention:
  • Critical alerts that require immediate attention
  • Voice-based 2FA for high-security scenarios
  • Appointment reminders with confirmation
  • Text-to-speech with natural voices
  • Call recording and transcription
  • Interactive voice response (IVR)
  • Global coverage with local numbers

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Quick Example

const response = await client.voice.call({
  from: '+1234567890',
  to: '+1987654321',
  message: 'Hello, this is a reminder about your appointment tomorrow at 2 PM. Press 1 to confirm or 2 to reschedule.',
  voice: 'alice', // Natural-sounding voice
  language: 'en-US'
});

console.log('Call initiated:', response.id);

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Voice Features

Text-to-Speech
  • Natural-sounding voices in multiple languages
  • Customizable speed and pitch
  • Support for SSML (Speech Synthesis Markup Language)
  • Pronunciation customization
Call Flow Control
  • Gather user input via keypad (DTMF)
  • Record caller responses
  • Transfer to live agents
  • Play hold music or messages
Analytics
  • Call duration tracking
  • Answer rate monitoring
  • Recording and transcription access
  • Failed call analysis

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Best Practices

Voice is the most intrusive channel. Use it only for urgent, high-priority communications.
State who you are and why you’re calling within the first few seconds.
Respect the recipient’s time. Get to the point quickly and provide clear next steps.
Always offer text/SMS alternatives for non-critical information.

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Unified API Patterns

All channels in Transmit follow consistent patterns:

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Consistent Response Format

{
  "id": "msg_abc123",
  "status": "queued",
  "channel": "email|sms|voice",
  "createdAt": "2025-01-10T14:23:45Z"
}

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Unified Status Model

StatusDescription
queuedMessage accepted and queued for sending
sendingCurrently being sent
sentSuccessfully handed off to carrier/provider
deliveredConfirmed delivery to recipient
failedFailed to deliver (with error details)
bouncedRejected by recipient server/carrier

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Consistent Error Handling

try {
  const response = await client.sms.send({ /* ... */ });
} catch (error) {
  if (error.code === 'invalid_phone_number') {
    // Handle invalid number
  } else if (error.code === 'rate_limit_exceeded') {
    // Handle rate limiting
  }
}

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Channel Selection Guide

Choose the right channel for your use case:
Use CaseRecommended ChannelWhy
Order confirmationsEmailRich content, receipt attachment
2FA codesSMSFast delivery, high open rate
Password resetsEmailClickable link, detailed instructions
Delivery notificationsSMSTime-sensitive, mobile-first
Critical system alertsVoice → SMS → EmailEscalating urgency
Monthly newsletterEmailRich content, images, links
Appointment remindersSMS + EmailSMS for urgency, email for details
Security breach alertVoice + EmailMaximum urgency and detail

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Multi-Channel Campaigns

Send coordinated messages across multiple channels: 
// Send confirmation email + SMS
const email = await client.emails.send({
  to: 'user@example.com',
  subject: 'Order Confirmed #1234',
  html: '<!-- detailed order confirmation -->'
});

const sms = await client.sms.send({
  to: '+1987654321',
  body: 'Order #1234 confirmed! Check your email for details.'
});

// Link them for unified tracking
await client.campaigns.link({
  campaignId: 'order-confirmation',
  messages: [email.id, sms.id]
});

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Webhooks Across All Channels

Receive real-time events for all channels with consistent payload structure: 
{
  "event": "message.delivered",
  "channel": "sms",
  "timestamp": "2025-01-10T14:23:45Z",
  "data": {
    "id": "msg_abc123",
    "to": "+1987654321",
    "status": "delivered",
    "deliveredAt": "2025-01-10T14:23:45Z"
  }
}

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Next Steps

Email Guide

Deep dive into email features

Analytics

Track performance across all channels

Webhooks

Set up real-time event notifications

API Reference

Complete API documentation
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