SMS Carrier Restrictions 2025: How Phone Validation Saves Your Campaigns

Step 1: Audit Your Current Database

Before sending another SMS, run your entire contact list through a phone validation API. This one-time cleanup typically reveals 23-40% invalid numbers.

POST /api/v1/validate
{
  "phone": "+12125551234",
  "country": "US",
  "type": "sms_compliance"
}

Response:
{
  "valid": true,
  "type": "mobile",
  "carrier": "Verizon",
  "canReceiveSMS": true,
  "riskScore": "low",
  "lastSeen": "2025-12-01"
}

Step 2: Implement Real-Time Validation

Integrate phone validation into your sign-up forms and CRM. This prevents invalid numbers from entering your database and ensures every new contact is SMS-ready.

// Frontend validation
const validatePhone = async (phone) => {
  const response = await fetch('/api/validate', {
    method: 'POST',
    body: JSON.stringify({ phone })
  });

  const result = await response.json();

  if (!result.valid || result.type !== 'mobile') {
    throw new Error('Please enter a valid mobile number');
  }

  if (!result.canReceiveSMS) {
    throw new Error('This number cannot receive SMS messages');
  }

  return result;
};

Step 3: Set Up A2P 10DLC Registration

Work with your SMS provider to complete A2P 10DLC registration. This includes brand verification, campaign registration, and trust score optimization.

Required Information:

• Business registration documents (EIN, formation papers)
• Website URL and business description
• Contact information and support details
• Sample messages for each campaign type
• Consent collection methodology documentation

Step 4: Create Your Compliance Workflow

Build an automated system that validates every number, checks consent, and monitors delivery rates. This workflow reduces compliance issues by 94%.

Step 5: Monitor and Maintain

Set up automated monitoring to track delivery rates, opt-out responses, and carrier feedback. React quickly to issues before they impact your sender reputation.

What happens if I don't register for A2P 10DLC?

Carriers will block your messages, throttle your sending speeds, and may suspend your SMS service entirely. Many carriers have already implemented mandatory A2P 10DLC checks, and non-compliant messages are being rejected at the network level.

How often should I validate my phone list?

For best results, validate in real-time during data entry and re-validate your entire list every 30-60 days. Phone status changes frequently—about 3-5% of numbers change status each month due to disconnections, porting, or carrier changes.

Can I send SMS to VoIP numbers?

It depends on the VoIP type. Fixed VoIP numbers (like Google Voice for Business) can typically receive SMS, but non-fixed VoIP numbers often cannot. More importantly, carriers flag high volumes of SMS to VoIP numbers as potential spam, which can hurt your sender reputation.

What's the difference between transactional and marketing SMS?

Transactional messages (order updates, appointments, alerts) don't require explicit marketing consent but must be transactional in nature. Marketing messages (promotions, sales, general marketing) require prior express written consent and have stricter sending time restrictions.

How do I prove consent if challenged?

Maintain detailed records including: opt-in method (web form, keyword, etc.), timestamp of consent, IP address for online opt-ins, clear disclosure of message frequency and type, and any terms and conditions the customer agreed to during sign-up.