📄️ Overview
Spam filtering is an essential component of any modern mail server, designed to sift through vast amounts of incoming email to identify and segregate unsolicited or potentially harmful messages. These unsolicited messages, commonly known as spam, not only clutter an individual's inbox but can also pose significant security risks. Efficient spam filtering ensures that genuine, legitimate emails reach their intended recipients, while unwanted or malicious emails are quarantined or discarded.
🗃️ Settings
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🗃️ Linear Classifier
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📄️ LLM Classifier
The LLM Classifier in Stalwart enhances the spam filtering capabilities by utilizing AI models to detect threats, unsolicited emails, and commercial messages. By integrating with any of the configured AI models, the LLM Classifier improves the accuracy of spam detection, analyzing the content of incoming messages through advanced natural language processing techniques. This approach allows the spam filter to better understand the nature of the emails and identify potential risks.
📄️ Rules
Stalwart supports custom spam filter rules to be defined, allowing administrators to analyze email messages and assign tags dynamically. These rules rely on expressions to evaluate different sections of an email, such as the headers, body, sender information, or attachments, and determine whether specific tags should be applied to identify potential spam.
📄️ DNS Blocklists
In the realm of email security and spam filtering, two powerful tools stand out for their efficacy in combating unsolicited messages: DNSBL (DNS-based Block List) and DNSWL (DNS-based Allowlist). DNSBLs and DNSWLs are maintained by various organizations and are updated in real-time to reflect the latest information about spam and malicious activity on the Internet. These tools utilize DNS (Domain Name System) queries to quickly and efficiently determine the reputation of sending IP addresses or domain names, aiding in the decision-making process of whether to accept, reject, or further scrutinize an incoming email.
📄️ DMARC Analysis
Ensuring the authenticity and integrity of incoming emails is paramount in modern email systems, given the prevalence of phishing and spoofing attacks. Stalwart incorporates a comprehensive mechanism to validate the authenticity of emails using four e-mail authentication standards: DMARC (Domain-based Message Authentication, Reporting, and Conformance), SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and ARC (Authenticated Received Chain).
📄️ Phishing Protection
Phishing is a deceptive technique employed by cybercriminals to trick individuals into revealing sensitive information, such as passwords, credit card numbers, and other personal details. Typically, these attacks use counterfeit emails, websites, or messages that appear to be from legitimate sources, luring the unsuspecting user into providing their data. As cyber threats evolve, phishing attempts have become more sophisticated, sometimes making them challenging to distinguish from genuine communications.
📄️ Collaborative Digests
In the evolving world of cyber threats, collaborative spam detection emerges as one of the most potent tools in the fight against unsolicited emails. By harnessing the power of distributed networks and collective intelligence, collaborative spam detection provides a dynamic and ever-updating defense mechanism against spam.
📄️ Trusted Senders
Trusted senders are mechanisms that take precedence over the spam filter’s final score and ensure that a message is delivered to the user’s inbox when specific trust conditions are met. These mechanisms are independent of the statistical classifier and apply at a higher decision level, providing deterministic guarantees for messages that are strongly associated with the user’s legitimate correspondence. Their purpose is to prevent false positives in cases where contextual knowledge is more reliable than statistical inference.
📄️ Greylisting
Greylisting is a method where an email server temporarily rejects emails from unknown senders. In essence, when an email from an unfamiliar source arrives, the server sends back a "try again later" message. Legitimate email servers, following standard email protocols, will attempt to resend the email after a short delay. Most spammers, on the other hand, don't bother with resending, and hence, the email never gets through.
📄️ Spamtrap
The ongoing war against spam requires innovative and multifaceted strategies. One such strategy, known as a spam trap, serves as a deceptive mechanism to lure in spammers, thereby allowing for the identification and mitigation of spam sources.