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SMTP Relay for reliable and secure email delivery

Send transactional emails securely, quickly and at scale – directly from your existing systems. With Maileon’s SMTP Relay, you benefit from powerful sending infrastructure, maximum deliverability and easy integration via SMTP or API. Whether it’s order confirmations, password resets or system notifications: make sure every important email reliably reaches your recipients.

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SMTP Relay

Automated emails are a central part of modern business processes. Whether it’s an order confirmation, login code or shipping notification, every message needs to be delivered quickly, securely and reliably. Instead of operating your own mail servers or investing resources in maintenance, monitoring and reputation management, Maileon takes care of the entire sending process. This reduces technical complexity, takes the strain off your IT team and creates the foundation for professional, scalable email communication.

bash

POST https://smtp-api.maileon.com/1.0/messages
Authorization: Basic YOUR_API_KEY
Content-Type: application/json

{
  "from": { "email": "no-reply@jouwdomein.nl", "name": "Your Company" },
  "to": [ { "email": "client@example.com" } ],
  "subject": "Welcome to Maileon!",
  "html": "<p>Hello {{firstname}}, welcome to our newsletter!</p>",
  "tags": ["welcome", "onboarding"],
  "substitution_data": { "firstname": "Kim" }
}

Maileon SMTP

With Maileon’s SMTP Relay, the entire sending process is handled through powerful infrastructure. Instead of operating your own mail servers or managing authentication, IP reputation and deliverability, your applications send emails securely and reliably via the Maileon platform. This reduces administrative effort, improves deliverability and creates the foundation for scalable email communication – regardless of sending volume.

SMTP Relay: How it works

1. Automatic email creation

Your application automatically creates an email – for example, an order confirmation, password reset or shipping notification.

2. Handover to the relay server

The message is securely transmitted to Maileon via the standardised SMTP protocol. Your existing application remains unchanged, while the technical sending process is handled via our platform.

3. Intelligent sending optimisation

Before delivery, Maileon handles authentication, reputation management and intelligent bounce handling. This creates the optimal conditions for secure and successful email delivery.

4. Successful delivery

The email is reliably transmitted to the recipient’s mail server. Modern sending mechanisms increase the likelihood that important messages will arrive directly in the inbox.

5. Transparent sending tracking

After sending, information on deliveries, bounces, opens and other events is available in real time. This gives you a complete overview of your email performance at all times.

6. Automatically process data further

Via webhooks or the REST API, sending and tracking data flows directly into your existing systems. This allows you to automate processes and efficiently extend your workflows.

Use Cases

From the first contact through to long-term customer engagement, automated emails are an important part of modern customer communication. With Maileon’s SMTP Relay, you can reliably and efficiently send important messages such as order confirmations, registrations, password resets, invoices and system notifications. Whether you operate an e-commerce business, SaaS platform, CRM system or custom application, Maileon integrates flexibly into your processes and provides a professional foundation for successful communication.

✓ Order confirmations
✓ Password resets
✓ Login codes
✓ Invoices
✓ Shipping notifications
✓ Registration confirmations
✓ Security alerts
✓ Appointment confirmations
✓ Status updates
✓ System notifications

🛒 E-Commerce
👤 Customer portals
💻 SaaS platforms
🏢 CRM & ERP
📱 Apps & platforms
⚙️ Custom software

Seamless integration with your existing systems & processes

Maileon’s SMTP Relay can be integrated quickly and easily into existing applications. We offer straightforward integrations for CRM, ERP, shop systems, customer portals and custom software.

For maximum flexibility, we support modern template languages such as Liquid, Jinja, Mustache and Handlebars. Dynamic content, personalised messages, automatic CSS inlining and text versions ensure optimal display across virtually all email clients. This allows you to integrate professional email delivery into your existing processes without extensive customisation.

Developed for the highest sending quality

Time-critical messages need to reach recipients without delay. That is why Maileon relies on a modern sending architecture that optimally combines speed, stability and security.

Dedicated IP addresses, intelligent bounce management, AddressCheck and continuous reputation management help to identify and prevent sending issues at an early stage and sustainably improve inbox placement. This means order confirmations, invoices, login codes and notifications reach their recipients reliably – even when sending volumes are high.

Enterprise-level data protection & security

Professional email communication requires the highest standards of security and data protection. That is why Maileon supports modern authentication methods and ensures that your messages are transmitted securely and clearly verified by receiving mail servers.

This is complemented by dedicated sending domains, continuous reputation management and GDPR-compliant processing of your data. This creates the foundation for secure, trustworthy and successful email delivery over the long term.

All benefits at a glance

Designed for professional email delivery

With Maileon, you benefit from a modern sending platform that combines security, performance and flexibility. Dedicated IP addresses, comprehensive analytics and versatile personalisation options provide the foundation for reliable and efficient email delivery – without the need for your own server infrastructure.

A solution that grows with your business

Whether you send a few hundred or several million emails per day, Maileon’s SMTP Relay adapts flexibly to your sending volume and maintains high performance at all times. This means deliverability and speed remain consistently high as your requirements grow.

Maximum Deliverability

Your emails reliably reach the inbox. Maileon’s optimised sending technology supports consistently high deliverability.
Seamless Integration

Connect the SMTP Relay easily via SMTP or REST API. Your existing applications remain unchanged.
Flexible Scalability

From small sending volumes to millions of emails per day, the platform grows with your requirements.
Strong Sender Reputation

Dedicated IP addresses and active reputation management build trust with receiving mail servers.
Live Tracking & Reporting

Analyse deliveries, opens and other sending events in real time – including reporting and webhooks.
Enterprise-Level Security

Modern authentication methods and up-to-date security standards reliably protect your email communication.
100% GDPR-Compliant

Benefit from a data protection-compliant solution that reliably meets regulatory requirements.
Reduced Operational Effort

Leave the operation and maintenance of your sending solution to Maileon and free up your internal resources.
REST API & Webhooks

Integrate sending data, status messages and events directly into your systems and automate your workflows.
Flexible SMTP Authentication

Supports current authentication methods for secure and reliable sending via your existing applications.

Try Maileon free for 30 days

Optimise your email delivery with a professional SMTP Relay solution. Benefit from easy integration, high performance and modern security standards – for automated messages that reliably reach their destination. Try Maileon today for 30 days – free of charge and with no obligation.

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SMTP Relay FAQ

What is an SMTP Relay?

An SMTP Relay is a service that sends emails on behalf of your applications or systems. Instead of operating your own mail server, messages are relayed through professional sending infrastructure. This improves deliverability, reduces administrative effort and enables secure, scalable email delivery – particularly for transactional emails such as order confirmations, password resets and notifications.

How does an SMTP Relay work?

When sending via an SMTP Relay, your application transmits the email to the relay server using the standardised SMTP protocol. The relay server then handles authentication, delivery and communication with the recipient’s mail server. Professional providers such as Maileon optimise delivery through continuous reputation management, modern security mechanisms and powerful infrastructure.

What is the difference between SMTP and SMTP Relay?

SMTP (Simple Mail Transfer Protocol) is the technical protocol used to send emails. An SMTP Relay, on the other hand, is the service that uses this protocol to reliably deliver messages via a professional sending platform. While SMTP merely describes the transmission standard, an SMTP Relay provides high deliverability, security, scalability and optimised sending performance.

When do I need an SMTP Relay?

An SMTP Relay is recommended whenever applications send automated or business-critical emails. These include:

Order confirmations
Password resets
Registration confirmations
Invoices
Shipping notifications
Security alerts
System notifications

The greater the sending volume or the more important reliable delivery is, the more businesses can benefit from a professional SMTP Relay solution.

What are the benefits of a professional SMTP Relay?

A professional SMTP Relay service offers much more than simply sending emails. Businesses benefit from:

high deliverability
scalable sending infrastructure
easy integration with existing systems
authentication according to current standards
detailed sending and performance analytics
reduced administrative effort
high levels of security and compliance

This allows businesses to focus on their core processes while the technical email delivery is handled reliably in the background.

Can I integrate the SMTP Relay with existing systems?

Yes. Maileon’s SMTP Relay can be easily integrated into existing applications. Whether it is a CRM, ERP, shop system or custom software, the use of the standardised SMTP protocol keeps integration simple and flexible. Alternatively, a REST API is available for more advanced requirements.

Does Maileon support personalised emails?

Yes. Dynamic content can be implemented using various template languages such as Liquid, Mustache, Handlebars or Jinja. In addition, individual data can be passed directly when sending, allowing personalised transactional emails to be created automatically – without any additional manual effort.

SMTP Relay or API – which solution is right for me?

Both options enable secure and reliable delivery of transactional emails. An SMTP Relay is particularly suitable for businesses that want to connect existing applications quickly and easily. A REST API, on the other hand, provides additional options for custom integrations, extensive automation and more detailed control over the sending process. The most suitable solution depends on your technical requirements and existing systems.

How does an SMTP Relay improve deliverability?

Professional SMTP Relay providers continuously invest in building and maintaining their sending infrastructure. This includes dedicated IP addresses, authentication methods, continuous reputation management, bounce management and comprehensive monitoring. These measures significantly increase the chances that important emails will arrive directly in the inbox rather than the spam folder.

Is Maileon’s SMTP Relay suitable for growing businesses?

Yes. Maileon’s SMTP Relay is designed for high sending volumes and scales flexibly with your business. Whether you are a start-up, medium-sized business or enterprise, the scalable infrastructure ensures consistently high performance and reliable delivery, even as sending volumes increase significantly.