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· 6 min read
Mauro D.

We are happy to announce the release of Stalwart Mail Server v0.10.3, which introduces support for AI models —a powerful new feature now available to Enterprise Edition users as well as our GitHub and OpenCollective sponsors. With this feature, Stalwart Mail Server can be integrated with both self-hosted and cloud-based Large Language Models (LLMs), bringing advanced email processing capabilities like never before.

This integration allows you to use AI models for a variety of tasks, including enhanced spam filtering, threat detection, and intelligent email classification. Whether you choose to host your own models with LocalAI or leverage cloud-based services like OpenAI or Anthropic, this release provides the flexibility to incorporate cutting-edge AI into your email infrastructure.

Unlocking the Power of AI

With the introduction of AI model integration, Stalwart Mail Server can now analyze email content more deeply than traditional filters ever could. For instance, in the realm of spam filtering and threat detection, AI models are highly effective at identifying patterns and detecting malicious or unsolicited content. The system works by analyzing both the subject and body of incoming emails through the lens of an LLM, providing more accurate detection and filtering.

In addition to bolstering security, AI integration enhances email classification. By configuring customized prompts, administrators can instruct AI models to categorize emails based on their content, leading to more precise filtering and organization. This is particularly useful for enterprises managing a high volume of messages that span various topics and departments, as AI-driven filters can quickly and intelligently sort messages into categories like marketing, personal correspondence, or work-related discussions.

The flexibility of using either self-hosted or cloud-based AI models means that Stalwart can be tailored to your infrastructure and performance needs. Self-hosting AI models ensures full control over data and privacy, while cloud-based models offer ease of setup and access to highly optimized, continuously updated language models.

LLMs in Sieve Scripts

One of the most exciting features of this release is the ability for users and administrators to access AI models directly from Sieve scripts. Stalwart extends the Sieve scripting language by introducing the llm_prompt function, which allows users to send prompts and email content to the AI model for advanced processing.

For example, the following Sieve script demonstrates how an AI model can be used to classify emails into specific folders based on the content:

require ["fileinto", "vnd.stalwart.expressions"];

# Base prompt for email classification
let "prompt" '''You are an AI assistant tasked with classifying personal emails into specific folders.
Your job is to analyze the email's subject and body, then determine the most appropriate folder for filing.
Use only the folder names provided in your response.
If the category is not clear, respond with "Inbox".

Classification Rules:
- Family:
* File here if the message is signed by a Doe family member
* The recipient's name is John Doe
- Cycling:
* File here if the message is related to cycling
* File here if the message mentions the term "MAMIL"
- Work:
* File here if the message mentions "Dunder Mifflin Paper Company, Inc." or any part of this name
* File here if the message is related to paper supplies
* Only classify as Work if it seems to be part of an existing sales thread or directly related to the company's operations
- Junk Mail:
* File here if the message is trying to sell something and is not work-related
* Remember that John lives a minimalistic lifestyle and is not interested in purchasing items
- Inbox:
* Use this if the message doesn't clearly fit into any of the above categories

Analyze the following email and respond with only one of these folder names: Family, Cycling, Work, Junk Mail, or Inbox.
''';

# Prepare the base Subject and Body
let "subject" "thread_name(header.subject)";
let "body" "body.to_text";

# Send the prompt, subject, and body to the AI model
let "llm_response" "llm_prompt('gpt-4', prompt + '\n\nSubject: ' + subject + '\n\n' + body, 0.6)";

# Set the folder name
if eval "contains(['Family', 'Cycling', 'Work', 'Junk Mail'], llm_response)" {
fileinto "llm_response";
}

This example demonstrates how the llm_prompt function can be used to classify emails into different categories such as Family, Cycling, Work, or Junk Mail based on the content. The AI model analyzes the message’s subject and body according to the classification rules defined in the prompt and returns the most appropriate folder name. The email is then automatically filed into the correct folder, making it easier to organize incoming messages based on their content.

Self-Hosted or Cloud-Based

With this new feature, Stalwart Mail Server allows for seamless integration with both self-hosted and cloud-based AI models. If you prefer full control over your infrastructure, you can opt to deploy models on your own hardware using solutions like LocalAI. Self-hosting gives you complete ownership over your data and ensures compliance with privacy policies, but it may require significant computational resources, such as GPU acceleration, to maintain high performance.

Alternatively, you can integrate with cloud-based AI providers like OpenAI or Anthropic, which offer access to powerful, pretrained models with minimal setup. Cloud-based models provide cutting-edge language processing capabilities, but you should be aware of potential costs, as these providers typically charge based on the number of tokens processed. Whether you choose self-hosted or cloud-based models, Stalwart gives you the flexibility to tailor the AI integration to your specific needs.

Available for Enterprise Users and Sponsors

This exciting AI integration feature is exclusively available for Enterprise Edition users as well as GitHub and OpenCollective monthly sponsors. If you want to harness the full potential of AI-powered email processing in Stalwart Mail Server, upgrading to the Enterprise Edition or becoming a sponsor is a great way to access this feature and other advanced capabilities.

Try It Out Today!

The release of Stalwart Mail Server v0.10.3 marks a major milestone in our journey toward building intelligent, highly customizable email management solutions. By combining traditional email filtering with the power of LLMs, Stalwart gives you the tools to take your email infrastructure to the next level, enhancing security, organization, and automation in ways that were previously impossible. We’re excited to see how you’ll use this new feature to optimize your email workflows!

· 4 min read
Mauro D.

Today we announce the release of Stalwart Mail Server v0.10.2, and it’s a big one! This version brings full OpenID Connect (OIDC) support, empowering admins and developers to integrate secure authentication and single sign-on (SSO) with modern identity providers. In addition to OIDC, this release introduces OpenID Connect Dynamic Client Registration, OpenID Connect Discovery, and OAuth 2.0 Token Introspection. Let’s dive into what these features are and why they matter.

What is OpenID Connect?

OpenID Connect (OIDC) is an identity layer built on top of OAuth 2.0 that allows clients to verify the identity of users. With OIDC, instead of just authorizing an app to access a resource, the system can also authenticate the user securely. This means users can log in to multiple applications with a single set of credentials, making OIDC ideal for Single Sign-On (SSO) across services.

Why is this important? Because it saves users from password fatigue, reduces login complexity, and centralizes authentication in a secure manner. Stalwart Mail Server’s new OIDC support allows you to authenticate your users either directly through Stalwart as an OpenID Provider or by integrating with third-party OIDC providers like Authentik, Keycloak, or any compliant identity system.

Alongside full OIDC support, Stalwart Mail Server v0.10.2 also introduces several important new features that expand its capabilities:

OpenID Connect Dynamic Client Registration

Dynamic Client Registration allows clients (applications) to automatically register with the OIDC provider without requiring manual intervention. This feature makes it easier to integrate multiple applications, as clients can dynamically obtain credentials (like client IDs) directly from Stalwart Mail Server. This adds flexibility and reduces administrative overhead.

OpenID Connect Discovery

With the OpenID Connect Discovery feature, clients can automatically discover the relevant OIDC endpoints and supported capabilities via the /.well-known/openid-configuration endpoint. This simplifies the configuration of OIDC clients, as they don’t need to be manually configured with URLs for token, authorization, and userinfo endpoints — they just query the discovery endpoint and set themselves up!

OAuth 2.0 Token Introspection

OAuth 2.0 Token Introspection allows resource servers (like APIs or mail servers) to validate access tokens provided by clients. This ensures that the token being used is still active, hasn’t expired, and has the right permissions attached. This is particularly useful for securing interactions between various services while verifying that tokens are still valid.

OpenID Provider or Third-Party OIDC Support

Stalwart Mail Server v0.10.2 can now act as an OpenID Provider (issuing ID tokens and managing authentication), which means your organization can use it to handle authentication for all your internal applications and services. Alternatively, Stalwart can also integrate with third-party OIDC providers, so you can delegate authentication to systems like Authentik or Auth0, while still using Stalwart to manage your email infrastructure.

This dual functionality gives you the flexibility to choose how you want to manage authentication while taking full advantage of OIDC's security features.

About OAUTHBEARER...

Now, let’s talk about mail clients and the OAUTHBEARER SASL mechanism. While Stalwart fully supports OIDC, the majority of mainstream mail clients (looking at you, Outlook, Thunderbird, and Apple Mail) still don’t support OAUTHBEARER for OAuth-based authentication. Sure, we’ve done our part by adding OpenID support to Stalwart — now it's up to the mail clients to follow suit and add proper support for OIDC authentication. Maybe one day, we’ll see these clients finally catch up, and we can all enjoy the seamless authentication experience that OIDC offers.

In the meantime, users of these clients will need to continue using App Passwords to access their email accounts. But hey, maybe this is the gentle nudge the developers of these clients need to jump on the OpenID bandwagon!

Try It Out

Stalwart Mail Server v0.10.2 is available now, so download it, upgrade your server, and start taking advantage of these new features! Whether you’re setting up Stalwart as your OpenID Provider or integrating with a third-party provider, this release gives you the tools to secure authentication with modern standards like OpenID Connect.

Happy mailing and happy authenticating!

· 4 min read
Mauro D.

We're excited to announce the release of Stalwart Mail Server version 0.9.3! Whether you're using the Community or Enterprise version of Stalwart Mail Server, this update brings powerful new features to enhance your email infrastructure's security, performance, and monitoring capabilities. Let's dive into what's new:

Comprehensive Dashboard

A major highlight of this release for Enterprise users is the introduction of the new Dashboard feature. This tool provides real-time insights into your server's operations, allowing you to monitor critical metrics and trends at a glance. The Dashboard is divided into five distinct sections: Overview, Network, Delivery, Security, and Performance. The Overview dashboard offers a comprehensive summary of general mail server statistics, giving you a quick snapshot of the server's health and activity. The Network dashboard focuses on the number of total and active connections, enabling you to monitor network traffic and identify potential issues with server load. The Delivery dashboard provides detailed information on mail flow, including queued messages and the number of messages sent and received, ensuring that your mail delivery processes are running smoothly. The Security dashboard is dedicated to tracking your server’s defenses, presenting statistics on banned IPs, blocked requests, and spam filtering effectiveness. Finally, the Performance dashboard allows you to monitor key performance indicators such as memory usage, database latency, and DNS latency, helping you optimize the server's performance and address any bottlenecks.

Customizable Alerts

Also new to the Enterprise version is the Alerts feature, which ensures that you are always in the loop when important metrics reach critical thresholds. Whether it's a spike in memory usage, an increase in queued messages, or any other significant change, Alerts can notify you via email or webhooks the moment these events occur.

Alerts are highly configurable, allowing you to set up complex conditions that trigger notifications only when specific combinations of metrics are met. For example, you could set an alert for when server memory usage exceeds a certain amount and the message queue count rises above a defined level, helping you to react swiftly and prevent potential disruptions.

Security Enhancements

Security remains a top priority in this release, and version 0.9.3 introduces two new features that enhance the defenses of both the Community and Enterprise versions.

RCPT Brute Force Protection

Enhance your server's security with our new RCPT brute force protection. This feature automatically bans IP addresses attempting to discover valid email recipients through brute force attacks—a common tactic used by spammers. By implementing this protection, Stalwart Mail Server adds another layer of defense to your email infrastructure, helping to maintain the integrity of your user list and prevent potential security breaches.

Loitering Connection Protection

Defend against SYN Flood attacks with our loitering connection protection. This smart feature blocks IP addresses that repeatedly keep connections open without meaningful activity, helping to prevent resource exhaustion attacks. By identifying and mitigating these potential threats, Stalwart Mail Server ensures that your server resources are used efficiently and remain available for legitimate email traffic.

Conclusion

Stalwart Mail Server version 0.9.3 is a significant step forward in our commitment to providing a secure, efficient, and easy-to-manage mail server solution. Whether you are leveraging the powerful new monitoring and alerting tools in the Enterprise version or benefiting from the enhanced security features available across both versions, this update offers valuable enhancements that will help you better manage and protect your mail server.

We encourage all users to upgrade to version 0.9.3 and take advantage of these exciting new features. As always, we remain dedicated to improving Stalwart Mail Server and providing you with the best possible tools to manage your email infrastructure.

Thank you for your continued support, and we look forward to bringing you more updates and features in the future!

· 3 min read
Mauro D.

We are thrilled to announce the release of Stalwart Mail Server version 0.9.1, which comes packed with significant enhancements to our telemetry capabilities. This release marks a major milestone in our ongoing efforts to provide robust and efficient monitoring and logging solutions, ensuring our users can achieve optimal server performance and reliability.

Enhanced Tracing

In previous versions of Stalwart, tracing and logging provided valuable insights but lacked the detail and comprehensiveness needed for thorough monitoring. With version 0.9.1, we have completely rewritten the tracing and logging layer, resulting in a faster and more detailed system. The new implementation leverages a lock-free data structure, enabling Stalwart to record thousands of events per second without impacting server performance. This major upgrade ensures that every significant event is captured, providing a comprehensive view of the server's operations.

Stalwart now generates over 600 different types of events, significantly expanding the granularity and depth of our telemetry data. These events can be sent to OpenTelemetry or Webhooks, offering flexibility in how they are processed and analyzed. Additionally, events can be recorded in log files, sent to journald, or written directly to the console, providing multiple avenues for accessing and utilizing this detailed information.

Comprehensive Metrics

The highlight of Stalwart Mail Server version 0.9.1 is the introduction of support for hundreds of different metrics. This enhancement enables administrators to gain deeper insights into the server's performance and health. Metrics can be exported to OpenTelemetry using a push mechanism, allowing for real-time monitoring and analysis. Alternatively, they can be collected using Prometheus via a pull method, integrating seamlessly with existing monitoring infrastructures.

This robust metrics support ensures that users can monitor a wide range of server parameters, from resource usage to request handling, enabling proactive maintenance and troubleshooting. By providing comprehensive metrics, Stalwart Mail Server empowers administrators to make informed decisions, optimize performance, and maintain high levels of reliability.

HTTP Access Controls

In addition to these telemetry improvements, Stalwart Mail Server version 0.9.1 introduces a highly requested feature: HTTP endpoint access controls. This new capability allows administrators to limit access to HTTP endpoints based on various criteria, such as remote IP or IP range, HTTP method, listener ID, and more. This fine-grained control enhances security and ensures that only authorized users can access specific server functionalities.

The introduction of HTTP endpoint access controls responds directly to user feedback, demonstrating our commitment to continually enhancing the server based on real-world needs and experiences. This feature provides an additional layer of security and customization, making Stalwart Mail Server more versatile and robust.

Conclusion

Stalwart Mail Server version 0.9.1 represents a significant leap forward in our telemetry capabilities, offering faster, more detailed tracing and logging, comprehensive metrics support, and new HTTP endpoint access controls. These improvements underscore our dedication to providing a powerful, efficient, and secure mail server solution.

Upgrade to version 0.9.1 today and experience the next level of telemetry with Stalwart Mail Server!

· 3 min read
Mauro D.

We are excited to announce a partnership between Stalwart Labs and Nextcloud, bringing together our state-of-the-art Stalwart Mail Server with the comprehensive Nextcloud suite. This collaboration marks a significant step forward in enhancing productivity, security, and user experience for our customers.

What This Means for You

Nextcloud will now also offer a version bundled with Stalwart Mail Server, providing users with a powerful, efficient, and secure email solution seamlessly integrated within the Nextcloud environment. This integration is designed to provide a cohesive and streamlined experience, allowing users to manage their email, files, and collaborative projects all in one place.

Key Benefits

  • Enhanced Productivity: With Stalwart Mail Server bundled into Nextcloud, users can effortlessly access their email and other Nextcloud apps, such as files, calendars, and tasks. This unified approach reduces the time and effort spent on managing multiple platforms.
  • Robust Security: Both Stalwart Labs and Nextcloud prioritize security. Our mail server brings industry-leading security features, including encryption and advanced threat detection, ensuring your communications remain safe and confidential.
  • Seamless Collaboration: Nextcloud is known for its powerful collaboration tools. Integrating Stalwart Mail Server enhances these capabilities, allowing for better coordination and communication within teams.
  • User-Friendly Interface: Our combined efforts focus on delivering an intuitive and user-friendly interface, making it easier for users to navigate and utilize the full potential of the integrated suite.

About Stalwart Mail Server

Stalwart Mail Server is a highly reliable and secure email server designed for modern businesses. With features such as spam filtering, encryption, and high availability, it provides an unparalleled email experience. Our server is built to handle the demands of any organization, ensuring your communications are always fast, reliable, and secure.

About Nextcloud

Nextcloud is the leading open-source software suite for file sharing and collaboration. It offers a wide range of tools for managing and sharing files, calendars, contacts, and more, all while maintaining the highest standards of security and privacy. Nextcloud is trusted by millions of users worldwide, from small businesses to large enterprises.

Looking Ahead

This partnership is just the beginning. We are committed to continuously improving and expanding our integrated solutions to meet the evolving needs of our users. Stay tuned for more updates and enhancements as we work together to bring you the best in productivity and security.

We invite you to explore the new integrated experience and see firsthand how Stalwart Mail Server and Nextcloud can transform the way you work. For more information, please visit our website or contact our team.

Thank you for your continued trust and support.

· 2 min read
Mauro D.

E-mail filtering is a crucial part of any modern mail server and, for this reason, we're excited to announce the addition of Milter support to Stalwart Mail Server. This update, driven by user feedback, allows the integration of both new and old Milter filters, supporting versions 2 and 6, which expands the server's capabilities in inspecting, filtering, or modifying emails during processing.

A milter, or "mail filter", is an extension to mail servers based on the Sendmail protocol. Milters allow third-party software to access mail messages as they are being processed in order to filter, modify, or annotate them. By using Milters, a mail server can utilize a variety of functionalities such as spam filtering, virus scanning, and other types of mail processing, beyond what is built into the mail server itself. Milters operate at the SMTP protocol level, which means they have access to both the SMTP envelope and the message contents.

This new feature not only responds to our users' needs but also ensures that Stalwart can work seamlessly with any existing setup. Whether you are seeking better spam protection, antivirus measures, or implementing specific processing rules, milter filtering has got you covered.

Learn more about milter filters and how to set them up in our documentation.

· 2 min read
Mauro D.

We’re excited to announce that Stalwart Labs has received a grant from the NGI0 Entrust Fund. This fund, established by NLnet with financial support from the European Commission’s Next Generation Internet programme, aims to support the development of innovative and secure technologies for the internet of the future.

The purpose of the grant is to support the completion of the development of Stalwart Mail server, an open-source mail server written in Rust that is designed to be simple to run, but at the same time, extremely secure, robust, and focused on privacy. The funds from this grant will cover the development of several new features that will make Stalwart Mail server even more useful and user-friendly.

The features that Stalwart Labs team will develop with the support of the NGI0 Entrust Fund include Stalwart SMTP, HTTP Listener / JSON Parsing refactoring, Store Refactoring, MinIO/S3 blob storage, Quota support, External authentication support, Catch-all addresses and aliases, JMAP Quota, JMAP Blob, JMAP Contacts, JMAP Calendars, JMAP Tasks, JMAP MDN, and the integration of SMTP, JMAP, and IMAP. Additionally, the grant will also cover security auditing, ensuring that Stalwart Mail Server is as secure and reliable as possible.

With the completion of these features, Stalwart Mail server will become an even more powerful tool for individuals and organizations looking for a secure and private email solution. We look forward to seeing the impact that this innovative technology will have on the future of email and online communication.

We are grateful to NLnet, and the European Commission’s Next Generation Internet programme for their support in the development of Stalwart Mail server. We believe that this grant will enable us to make significant progress in the development of this important open-source project, and we look forward to sharing our progress with the community in the coming months.

· One min read
Mauro D.

It’s official! We are proud to announce the release of Stalwart SMTP, the next-generation email server solution written in Rust for businesses, organizations, and individuals alike.

Stalwart SMTP is a robust and secure email server that offers a comprehensive set of features to meet the needs of today’s demanding email communications. Whether you’re running a large enterprise or a small business, Stalwart SMTP is designed to handle the most complex email environments with ease.

One of the key features of Stalwart SMTP is its support for advanced email security protocols, including DMARC, DKIM, SPF, ARC, DANE, MTA-STS, and SMTP TLS reporting. This means that you can be sure that your emails are protected from spoofing and phishing attempts, and that your email messages are delivered securely to their intended recipients.

We are confident that Stalwart SMTP will meet the needs of businesses and organizations of all sizes, and we look forward to hearing your feedback and suggestions. To learn more about Stalwart SMTP, visit our website and start exploring the many features and benefits of this powerful email server solution.