BUILT FOR DEVELOPERS, CODED FOR SIMPLICITY
Brilliantly simple Messaging APIs for global scale
Whether you’re looking to unlock multichannel scale through our REST API, or achieve high SMS throughput and reliability with our SMPP Protocol, our messaging API Product Suite is built for immediate deployment.
Built for outcomes and coded for simplicity, our API Product Suite is backed with intuitive documentation and local human support included as standard.
What are messaging APIs?
Messaging APIs are integrations that streamline the connection between your existing tech stack and customer communication channels. They accelerate deployment, increase operational efficiency, and improve alignment across departments. The Esendex API Product Suite connects seamlessly to your CRM system, or another core software, centralising your customer communication.
How our messaging API Product Suite helps you scale
Our API suite lets you scale message volumes and expand into new channels by updating a single JSON parameter, eliminating API sprawl and reducing maintenance overheads. As an ISO 27001 and Cyber Essentials certified supplier, our integration allows you to grow securely, with concerns of UK regulatory compliance.
Turn APIs into your competitive advantage
35%
More likely to outperform competitors in operational efficiency.
Aspire systems
80%
Process automation rate achieved through API-driven workflows.
API Conference
65%
Of organisations are leveraging API programs as direct revenue drivers.
Postman
93%
Of all modern web apps and CRMs are powered by REST architecture.
Postman
Why Developers choose Esendex’s API Product Suite
Built for outcomes
Our multichannel REST API future-proofs your operations and eliminates API complexity with its modern architecture: one format, one base URL, and one API key.
Multichannel agility
Unlock multichannel scalability and unify channel orchestration by transitioning from SMS to RCS with one simple parameter change.
Fast integration
Reduce time-to-value and skip complex setup. Our modern architecture means you can set up your API in as little as 3 hours1, with dedicated local support included as standard.
Enterprise-grade security
Rest easy with a ISO 27001 and Cyber Essentials certified supplier, supported by proactive 24/7 vulnerability scanning built to strict OWASP guidelines
Local, human support included
Direct access to UK-based support, with over 20+ years experience – bypassing premium paywalls and expensive support-tier subscriptions.
Universal, global reach
Send messages worldwide with confidence. Our direct carrier connections and in-country knowledge ensure reliable delivery across borders.
“The Esendex range of products greatly enhance the way we speak with our customers from sales follow-ups and engineer appointment confirmations, all the way through to general Q&As.”
Arron Alderson – Solutions and Process Manager, Vaillant
One API Product Suite, two brilliantly simple integration options
Our API Product Suite offers a unified approach through two core integration options: our multichannel REST API and the powerful SMPP Protocol. Combining these together unlocks the power of engaging RCS messaging, the throughput of up to 50,000 SMS sends with the security of an ISO 27001-accredited and Cyber Essentials certified partner.
Unlock multichannel capabilities through our REST API
The Esendex multichannel REST API allows teams to dispatch SMS messages and automate rich media RCS messages over secure HTTPS.
Our REST API delivers rapid connectivity that enables simple, multichannel integration, by switching from SMS to RCS messaging with a single peramater change.
Key benefits of our multichannel REST API:
- Unify channel orchestration: Transition seamlessly between SMS and RCS with one parameter change.
- Reduce time-to-value: Go from setup to live sending within 3 hours1.
- Remove developer friction: Built with one JSON format, one base URL, and one API key.
Achieve high-volume SMS throughput with our SMPP Protocol
Our robust SMPP Protocol is the foundation for heavy-duty, mission-critical SMS outreach, allowing teams to control messaging traffic, stream high-volume sends over direct connections, and receive real-time insights without performance bottlenecks.
Perfect for high-volume, repetitive messaging such as system updates, promotional broadcasts, and internal operational alerts.
Key benefits of our SMPP Protocol:
- High-throughput streaming: Reach thousands of recipients in one send with ultra-low latency.
- Uninterrupted connectivity: Send messages without interruption with SMPP’s BIND architecture
- Enhanced security and reliability: Secured via mandatory TLS 1.2+ or VPNs.
What channels are available with our multichannel REST API?
Simply change a single JSON parameter to switch between SMS and RCS messaging.
RCS Business Messaging
Replace standard text-only messages with the functionality of a dedicated mobile app with high-res media, branding, and interactive buttons, delivered to native messaging apps across both iOS and Android, with no extra app download required.
Popular use cases include:
- Marketing promotions
- Security and 2FA messages
- Inbound customer support
- Booking and appointment reminders
SMS
Reach customers in seconds with text message alerts, reminders and marketing camapigns, with universal global reach.
Popular use cases include:
- OTPs and verification codes
- Delivery updates and reminders
- Welcome messages
- Broadcast business updates
Trust, compliance and reliability
Every message sent through Esendex carries a verified business profile, so customers can see who they’re really talking to. Messaging is handled under the same GDPR-aligned processes and ISO 27001-certified infrastructure as the rest of the Esendex platform.
How fast can you send your first SMS?
Sign up for your free trial, grab your API key, and dispatch your first SMS via our multichannel REST API in under 5 minutes flat2. Or click here to watch our engineer complete it in less than 3 minutes.
Prepare
0> Open your API client (e.g. Postman) in the background1> Get your device ready to Authenticate through MFA
// Making sure you are ready
Resources
Browsing through our Developer Documentation⮺ will help you to prepare.
// Your place for reference and code
5-Minute Challenge
0> Start your timer 1> Sign up⮺ for an Esendex account2> Create an API Key3> Send an SMS to yourself
// Free for 7-days && no commitment
Built by developers, coded for simplicity.
Our intuitive developer documentation enables teams to go from zero to sending in under 3 hours1. Skip the complex setup and benefit from simple modern architecture with world-class documentation and free, local, human support.
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API documents
API documentsWorld-class documentation and copy-pasteable code samples that are designed for multichannel immediate deployment.
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Not a developer?
Not a developer?Our brilliantly simple, intuitive developer documents are easy to read and understand, even without a technical background.
Getting started with the Esendex API Product Suite
Our intuitive developer documenation has been designed to make integration brilliantly simple, even for those without a technical background. You’ll find copy-pasteable code samples, quick start guides, full endpoint documentation, webhooks and more on our developer site.
Sending your first message
Ready to send your first message? Follow our guide to learn more about our API headers, parameters and request body.
Authentication
Esendex APIs use API Key access to authenticate requests. Once you have access to your account, you will be able to create, use and manage your API Key tokens via the Esendex Portal.
Base URL
The API is served over HTTPS to ensure data privacy, unencrypted HTTP is not supported.
Prerequisites
Our APIs are built on a RESTful endpoint structure and served using HTTPS to ensure data privacy; unencrypted HTTP is not supported.
Recipient number format
The telephone number of the message recipient must be in E.164 format.This means any recipient number provided must be in the format:+{Country Dial Code}{Rest of phone number})
IP addresses
Our API platform is offered from a globally distributed infrastructure, so you won’t be able to whitelist the IP addresses of our platform.
Rate limiting
Rate limiting restricts the number of API calls which can be made within a defined time period. Rate limiting acts as a basic security measure against malicious attacks and ensures an even flow of messages through the platform.
Versioning
The Esendex API includes the version being used in the URL. When backwards-incompatible changes are made to the API, a new version is released.
How fast can you send your first SMS?
Take on our 5-minute challenge
Sign up for your free trial, grab your API key, and dispatch your first SMS via our REST API in under 5 minutes flat2.
Sign up for your free trial
Watch our attempt
Watch our engineer complete it in under 2 minutes and 20 seconds.
Developer FAQs
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What’s the difference between the REST API and SMPP Protocol?
What’s the difference between the REST API and SMPP Protocol?REST is the fastest way to integrate: JSON over HTTPS, one API key, works with any modern language. SMPP is a binary protocol built for very high-throughput SMS, typically used by telecoms and aggregator-scale senders already running SMPP infrastructure. Most new integrations use REST.
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Which channels can I send through one API?
SMS and RCS run through the same authenticated request structure, so adding a channel is a parameter change, not a new integration.
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Is there a sandbox or test environment?
Yes – your free trial account includes test credits so you can send real messages to real numbers before committing to a paid plan, and delivery reporting works the same way in trial as in production.
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How do I get real-time delivery and inbound message events?
Subscribe to webhooks for delivery status, inbound replies and other account events instead of polling the API – set-up takes a few minutes through the Developer Portal.
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What are the rate limits?
Rate limits scale with your account tier – see current limits in the API Reference, or talk to your account manager if you’re planning a high-volume send.
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How is the API priced?
Pricing is usage-based per message and varies by channel and destination – see the pricing page for current rates, or get in touch for volume pricing.
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Do I need to be a developer to use Esendex?
Not at all! Our intuitive developer documents are designed to be brilliantly simple, with copy-pasteable code samples and our modern API architecture, meaning they can be understood and deployed even without a technical background.
1 From Account setup and verification to first successful API SMS send. Based on the average time taken for a new REST API Prepay customer (03/25 – 05/26
2 Based on our fastest customer integration time from free trial sign-up to first successful SMS message sent via API and independent in house testing.
Insights
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Idempotency keys and why your retry logic needs them
APIA timeout doesn’t mean the request failed. Without idempotency, your retry might send the same message twice.![]()
Webhooks vs polling: choosing a delivery receipt strategy
DevelopersPolling is easier to build and harder to live with. Here’s how to decide which approach fits your volume and latency requirements.![]()
Sending your first SMS with the Esendex API
DevelopersA five-minute walkthrough from API key to delivered message, with curl examples you can paste straight into a terminal.
