This document provides an overview of the SMS messaging guidelines for businesses using Carrick Health's services. It outlines the throughput and volume limits imposed by carriers, the different types of messaging options available, and best practices for ensuring successful message delivery.

When sending SMS messages through Carrick Health using U.S. phone numbers, message delivery is subject to carrier-imposed throughput and volume limits. These limits are designed to:

• Reduce spam and fraud

• Protect carrier networks

• Improve deliverability

• Ensure compliant messaging practices

The exact limits depend on the type of phone number being used:

• A2P 10DLC Numbers

• Toll-Free Numbers

Each messaging type has different registration requirements, throughput limits, and carrier policies.

Message throughput is measured in Messages Per Second (MPS). MPS determines how quickly messages can be sent from a phone number or messaging campaign. Carrick Health measures throughput using message segments, not individual messages. A standard SMS segment contains up to 160 GSM-7 characters. Longer messages may be split into multiple segments, which count separately toward throughput limits.

A2P 10DLC (Application-to-Person 10-Digit Long Code) is the standard system for business messaging using local U.S. phone numbers. All businesses using 10DLC numbers for SMS messaging must register:

• A business brand

• A messaging campaign

• An approved messaging use case

Registration must be completed through Carrick Health and The Campaign Registry (TCR).

Low Volume Mixed campaigns are designed for businesses with lower messaging requirements and mixed-use traffic such as:

• Customer communication

• Notifications

• Light marketing

• Conversational messaging

Low Volume Mixed campaigns support approximately:

• Up to 2,000 SMS segments and MMS messages per day toward T-Mobile

• Approximately 6,000 SMS segments and MMS messages per day across U.S. carriers

These campaigns also receive lower throughput than standard declared-use campaigns.

Toll-Free SMS messaging allows businesses to send and receive text messages using Toll-Free numbers in the United States and Canada. Unlike A2P 10DLC messaging, Toll-Free messaging does not require campaign registration through The Campaign Registry (TCR). Instead, businesses must complete Toll-Free Verification.

Toll-Free Verification helps carriers confirm:

• Your business identity

• Intended messaging use case

• Opt-in process

• Sample message content

• Compliance with carrier messaging policies

Verification improves deliverability and reduces carrier filtering.

Verified Toll-Free numbers support approximately:

Higher throughput may be available for approved high-volume use cases. If you are interested in higher throughput, please contact support. Actual throughput may vary depending on:

• Carrier policies

• Sending reputation

• Traffic consistency

• Recipient engagement

• Message content

• Compliance history

When launching a new Toll-Free number, it is important to gradually increase messaging volume over time. This process is commonly referred to as warming up your number. Carriers monitor new messaging traffic closely for spam prevention and compliance purposes. Sudden spikes in outbound SMS volume from a newly verified Toll-Free number may increase the likelihood of:

• Carrier filtering

• Message delays

• Temporary throttling

• Reduced deliverability

Gradually increasing message volume helps establish a positive sending reputation with carriers.

For newly verified Toll-Free numbers, a gradual ramp-up strategy is strongly recommended. A common best-practice approach is:

These are not official limits enforced by Twilio, but industry best practices designed to help establish healthy carrier trust and reduce filtering risk.

If messaging traffic exceeds acceptable carrier thresholds:

• Messages may be queued

• Delivery speeds may slow down

• Carriers may throttle or filter traffic

• Carrick Health may temporarily restrict outbound messaging

Traffic spikes, inconsistent sending patterns, and poor opt-in practices can increase the likelihood of carrier filtering. For A2P 10DLC campaigns, error code 30023 may be returned when daily limits are reached.

To maintain healthy delivery rates and avoid filtering, it is essential to:

• Send messages only to opted-in recipients

• Avoid sudden traffic spikes

• Use consistent sending patterns

• Clearly identify your business in messages

• Avoid misleading or spam-like content

• Maintain accurate consent records

• Use messaging content consistent with your registered campaign use case