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Bulgaria SMS Best Practices, Compliance, and Features

Bulgaria SMS Market Overview

Locale name:	Bulgaria
ISO code:	BG
Region	Europe
Mobile country code (MCC)	284
Dialing Code	+359

Market Conditions: Bulgaria has a mature mobile market with high SMS adoption rates. The country's main mobile operators include A1 Bulgaria, Telenor Bulgaria, and Vivacom. While OTT messaging apps like WhatsApp and Viber are popular, SMS remains crucial for business communications and authentication purposes. The market shows a relatively even split between Android and iOS users, with Android having a slight edge in market share.

Key SMS Features and Capabilities in Bulgaria

Bulgaria supports most standard SMS features including concatenated messages and number portability, though two-way SMS functionality is limited.

Two-way SMS Support

Two-way SMS is not supported in Bulgaria through major SMS providers. This limitation affects interactive messaging campaigns and automated response systems.

Concatenated Messages (Segmented SMS)

Support: Yes, concatenation is supported, though availability may vary by sender ID type.
Message length rules: Standard SMS length limits apply - 160 characters for GSM-7 encoding, 70 characters for UCS-2 encoding.
Encoding considerations: Both GSM-7 and UCS-2 encodings are supported. Messages using special characters will automatically use UCS-2 encoding, reducing the character limit per segment.

MMS Support

MMS messages are automatically converted to SMS with an embedded URL link. This conversion ensures delivery while maintaining rich media sharing capabilities through web-based content delivery.

Recipient Phone Number Compatibility

Number Portability

Number portability is available in Bulgaria. This feature allows users to keep their phone numbers when switching between mobile operators, with minimal impact on SMS delivery or routing.

Sending SMS to Landlines

Sending SMS to landline numbers is not possible in Bulgaria. Attempts to send messages to landline numbers will result in a failed delivery and typically generate a 400 response error (code 21614) through SMS APIs.

Compliance and Regulatory Guidelines for SMS in Bulgaria

Bulgaria follows EU telecommunications regulations and GDPR requirements for SMS communications. The Communications Regulation Commission (CRC) oversees telecommunications activities, while the Commission for Personal Data Protection (CPDP) enforces data privacy regulations.

Explicit Consent Requirements:

Written or electronic consent must be obtained before sending marketing messages
Consent records must be maintained and easily accessible
Purpose of communication must be clearly stated during opt-in
Double opt-in recommended for marketing campaigns

HELP/STOP and Other Commands

STOP commands must be supported in both Bulgarian and English
Common keywords include: STOP, ОТКАЗ, КРАЙ
All marketing messages must include opt-out instructions
HELP responses should be provided in Bulgarian by default

Do Not Call / Do Not Disturb Registries

Bulgaria does not maintain a centralized Do Not Call registry. However, businesses must:

Maintain their own suppression lists
Honor opt-out requests within 24 hours
Keep records of opted-out numbers for at least 2 years
Regularly clean contact lists against internal opt-out databases

Time Zone Sensitivity

Bulgaria observes Eastern European Time (EET/EEST). Best practices include:

Sending messages between 9:00 AM and 8:00 PM local time
Avoiding messages on national holidays
Limiting urgent messages outside business hours to genuine emergencies

Phone Numbers Options and SMS Sender Types for in Bulgaria

Alphanumeric Sender ID

Operator network capability: Supported
Registration requirements: Pre-registration not required, but dynamic usage is supported
Sender ID preservation: Yes, except for A1 and Vivacom Bulgaria where generic Alphanumeric IDs may be used

Long Codes

Domestic vs. International:

Domestic long codes not supported
International long codes supported

Sender ID preservation: No, international numbers may be overwritten with generic Alphanumeric IDs
Provisioning time: Immediate to 24 hours
Use cases: Transactional messages, alerts, and notifications

Short Codes

Support: Not currently supported in Bulgaria
Provisioning time: N/A
Use cases: N/A

Restricted SMS Content, Industries, and Use Cases

Restricted Industries:

Unauthorized gambling services
Adult content or services
Unlicensed financial services
Cryptocurrency promotions without proper disclaimers
Unauthorized pharmaceutical products

Content Filtering

Carrier Filtering Rules:

Messages containing certain keywords may be blocked
URLs should be from reputable domains
Avoid excessive capitalization and special characters

Best Practices to Avoid Filtering:

Use clear, professional language
Avoid spam trigger words
Include company name in sender ID
Keep URLs short and legitimate

Best Practices for Sending SMS in Bulgaria

Messaging Strategy

Keep messages under 160 characters when possible
Include clear call-to-actions
Personalize messages using recipient's name or preferences
Maintain consistent brand voice

Sending Frequency and Timing

Limit to 2-4 messages per month per recipient
Respect Bulgarian holidays and Orthodox Christian observances
Avoid weekends unless specifically requested
Space out messages to prevent recipient fatigue

Localization

Primary language should be Bulgarian
Consider dual-language messages for international businesses
Use proper character encoding for Cyrillic alphabet
Respect local cultural nuances and customs

Opt-Out Management

Process opt-outs immediately
Maintain clear opt-out records
Provide confirmation of successful opt-out
Regular audit of opt-out lists

Testing and Monitoring

Test across all major Bulgarian carriers (A1, Telenor, Vivacom)
Monitor delivery rates by carrier
Track engagement metrics
Regular testing of opt-out functionality

SMS API integrations for Bulgaria

Twilio

Twilio provides a robust SMS API with comprehensive support for Bulgarian numbers. Here's how to implement it:

import * as Twilio from 'twilio';

// Initialize client with your credentials
const client = new Twilio(
  process.env.TWILIO_ACCOUNT_SID,
  process.env.TWILIO_AUTH_TOKEN
);

// Function to send SMS to Bulgaria
async function sendBulgarianSMS(
  to: string,
  message: string,
  senderId: string
) {
  try {
    // Validate Bulgarian phone number format
    if (!to.startsWith('+359')) {
      throw new Error('Invalid Bulgarian phone number format');
    }

    const response = await client.messages.create({
      body: message,
      to: to,          // Bulgarian number in E.164 format
      from: senderId,  // Your registered sender ID
      // Optional parameters for delivery tracking
      statusCallback: 'https://your-webhook.com/status'
    });

    return response.sid;
  } catch (error) {
    console.error('SMS sending failed:', error);
    throw error;
  }
}

Sinch

Sinch offers reliable SMS delivery to Bulgaria with support for Unicode characters:

import { SinchClient } from '@sinch/sdk-core';

// Initialize Sinch client
const sinchClient = new SinchClient({
  servicePlanId: process.env.SINCH_SERVICE_PLAN_ID,
  apiToken: process.env.SINCH_API_TOKEN,
  region: 'eu'  // Use EU region for Bulgaria
});

async function sendSinchSMS(
  recipientNumber: string,
  messageText: string
) {
  try {
    const response = await sinchClient.sms.batches.send({
      to: [recipientNumber],
      from: 'YourBrand',  // Alphanumeric sender ID
      body: messageText,
      // Enable delivery reports
      deliveryReport: 'summary'
    });

    return response.id;
  } catch (error) {
    console.error('Sinch SMS failed:', error);
    throw error;
  }
}

MessageBird

MessageBird provides high-throughput SMS delivery for Bulgarian numbers:

import * as messagebird from 'messagebird';

// Initialize MessageBird client
const mbClient = messagebird(process.env.MESSAGEBIRD_API_KEY);

// Function to send SMS with delivery tracking
async function sendMessageBirdSMS(
  to: string,
  message: string
): Promise<string> {
  return new Promise((resolve, reject) => {
    mbClient.messages.create({
      originator: 'YourBrand',
      recipients: [to],
      body: message,
      // Optional parameters
      reportUrl: 'https://your-webhook.com/delivery',
      encoding: 'auto'  // Automatically handle Unicode
    }, (err, response) => {
      if (err) reject(err);
      else resolve(response.id);
    });
  });
}

Plivo

Plivo offers competitive rates for Bulgarian SMS with detailed delivery insights:

import * as plivo from 'plivo';

// Initialize Plivo client
const plivoClient = new plivo.Client(
  process.env.PLIVO_AUTH_ID,
  process.env.PLIVO_AUTH_TOKEN
);

async function sendPlivoSMS(
  destination: string,
  message: string
) {
  try {
    const response = await plivoClient.messages.create({
      src: 'YourBrand',  // Your sender ID
      dst: destination,  // Destination number
      text: message,
      // Optional parameters
      url: 'https://your-webhook.com/status',
      method: 'POST'
    });

    return response.messageUuid[0];
  } catch (error) {
    console.error('Plivo SMS failed:', error);
    throw error;
  }
}

API Rate Limits and Throughput

Twilio: 100 messages per second
Sinch: 30 messages per second
MessageBird: 60 messages per second
Plivo: 50 messages per second

Throughput Management Strategies:

Implement exponential backoff for retry logic
Use queue systems (Redis, RabbitMQ) for high-volume sending
Batch messages when possible (up to 500 recipients per request)
Monitor delivery rates and adjust sending patterns accordingly

Error Handling and Reporting

Implement comprehensive logging with Winston or Bunyan
Track delivery rates and failures by carrier
Set up automated alerts for unusual error rates
Store delivery receipts for audit purposes
Implement circuit breakers for API failures

Recap and Additional Resources

Key Takeaways:

Always use E.164 format for Bulgarian numbers (+359)
Implement proper error handling and retry logic
Monitor delivery rates and adjust sending patterns
Maintain compliance with GDPR and local regulations

Next Steps:

Review the Communications Regulation Commission guidelines
Implement proper consent management systems
Set up monitoring and alerting for SMS delivery
Test thoroughly across all major Bulgarian carriers

Additional Resources:

American Samoa SMS Guide