How to Send SMS Messages Using AWS Lambda, SNS, and Python

Introduction

This article explains how to send and receive SMS messages using AWS services. You will learn how to:

Receive SMS messages and log their content

Reply automatically to incoming messages (SMS echo)

Send scheduled SMS messages

All examples use AWS Lambda, SNS, and Amazon Pinpoint, with Python 3 as the programming language.

For simplicity, this guide uses the AWS Management Console (ClickOps). In real production environments, these resources should be managed using tools like Terraform, CloudFormation, CI/CD pipelines, and version control.

Why Use AWS Lambda for SMS?

AWS Lambda is a serverless compute service that lets you run code without managing servers.

Key benefits:

No server provisioning or maintenance

Fast deployment

Very low cost (first 1 million requests per month are free)

Scales automatically

Lambda works well for lightweight tasks such as processing SMS messages.

About SMS and Cost Considerations

SMS (Short Message Service) is widely supported but relatively expensive compared to internet-based messaging.

Typical costs (US region):

Receive SMS: ~$0.0075 per message

Send SMS: ~$0.00645 per message

For example:

Sending 1 SMS per day to 1,000 users can cost nearly $200/month

SMS is best used for:

One-time passwords (OTP)

Account verification

Critical alerts

Receiving SMS Messages

Step 1: Create a Lambda Function

Log in to AWS Console

Open AWS Lambda

Click Create Function

Choose:

Runtime: Python 3

Permissions: Create a new role with basic Lambda permissions

Create the function

Step 2: Add SNS as a Trigger

In the Lambda Designer, add SNS as a trigger

Allow SNS to invoke the Lambda function

Save the function

SNS will deliver incoming SMS messages to your Lambda function.

Step 3: Write Lambda Code to Log Messages

This basic function extracts:

Sender phone number

SMS text content and logs them to CloudWatch.

import json

def lambda_handler(event, context): message = json.loads(event['Records'][0]['Sns']['Message']) text = message['messageBody'] number = message['originationNumber']

return { 'statusCode': 200, 'body': json.dumps( f"Phone number: {number}\nMessage Text: {text}" ) }

Step 4: Test the Function

You can test the function without real SMS by creating a Lambda test event using the SNS template and providing a sample message payload.

Sending SMS Messages

To send SMS messages, AWS uses Amazon Pinpoint.

Step 1: Create a Pinpoint Project

Open Amazon Pinpoint

Create a new project

Enable SMS and Voice

Request a long code (dedicated phone number)

Long codes cost around $1 per month, so delete them when testing is complete.

Step 2: Update IAM Permissions

Add Pinpoint permissions to the Lambda execution role so the function can send SMS messages.

Step 3: Create an SMS Echo Function

This function replies with the same text it receives.

import json
import boto3
pinpoint = boto3.client('pinpoint')

def lambda_handler(event, context): message = json.loads(event['Records'][0]['Sns']['Message'])

pinpoint.send_messages( ApplicationId='YOUR_PINPOINT_APPLICATION_ID',
 MessageRequest={ 'Addresses': { message['originationNumber']: 
{'ChannelType': 'SMS'} },
 'MessageConfiguration': { 'SMSMessage': { 'Body': message['messageBody'], 
'MessageType': 'PROMOTIONAL' } } } )

This sends the reply using the Pinpoint long code.

Sending Scheduled SMS Messages:

You can also send SMS messages on a schedule using CloudWatch Eventbridge.

Daily reminders

Alerts

Notifications

Example

import json 
import boto3 
import random

pinpoint = boto3.client('pinpoint')

def lambda_handler(event, context): messages = [ "Sorry, I’m stuck in traffic.", "Running late due to car trouble.", "Had a family emergency this morning.", "Delayed due to work last night." ]

pinpoint.send_messages( ApplicationId='YOUR_PINPOINT_APPLICATION_ID', MessageRequest={ 'Addresses': { 'BOSS_PHONE_NUMBER': {'ChannelType': 'SMS'} }, 'MessageConfiguration': { 'SMSMessage': { 'Body': random.choice(messages), 'MessageType': 'PROMOTIONAL' } } } )

Trigger this function using a scheduled CloudWatch rule.

Summary:

In this guide, you learned how to use AWS services to send and receive SMS messages.

Services Used:

AWS Lambda – serverless function execution

SNS – receiving SMS messages

Amazon Pinpoint – sending SMS and managing phone numbers

IAM – permissions and security

CloudWatch – logs, monitoring, and scheduling