Amavisd-new is an open-source content filtering system designed to integrate with popular Mail Transfer Agents (MTAs) such as Postfix, Exim, and Sendmail. It provides a robust and customizable solution for email filtering, including spam detection, virus scanning, and content analysis. Here’s an overview of Amavisd-new and its key features:
1. Integration with MTAs: Amavisd-new acts as a bridge between the MTA and various content filtering components. It intercepts incoming and outgoing emails, performs filtering tasks, and then passes the messages back to the MTA for further processing.
2. Spam Detection: Amavisd-new incorporates multiple spam detection techniques, including pattern matching, Bayesian filtering, and DNS-based blacklists (DNSBLs). It examines various email attributes, content, and sender reputation to classify messages as spam or non-spam.
3. Virus Scanning: Amavisd-new integrates with popular antivirus engines, such as ClamAV, Sophos, and others, to perform real-time virus scanning of email attachments and embedded content. It helps prevent the distribution of malware and viruses through email.
4. Content Analysis: Amavisd-new supports content analysis for detecting malicious or undesirable content in email messages. It can be configured to examine attachments, URLs, HTML code, and other elements to identify potential threats or policy violations.
5. Greylisting: Amavisd-new includes greylisting functionality, a technique that temporarily rejects incoming emails from unknown senders. Legitimate servers usually retry the delivery, while many spam senders do not. This helps in reducing spam volume.
6. Flexible Policy Framework: Amavisd-new provides a flexible policy framework that allows administrators to define their own filtering policies and rules. It supports customizations such as whitelisting, blacklisting, header checks, and custom script execution.
7. Quarantine and Notification: Amavisd-new can be configured to quarantine suspicious or potentially harmful messages instead of outright rejection. It can notify administrators or users about quarantined messages, allowing manual review and release if necessary.
8. Logging and Reporting: Amavisd-new generates detailed logs and reports, providing insights into the filtering process. It records information about the filtering decisions made for each email, enabling administrators to analyze the effectiveness of the filtering system.
Amavisd-new is highly extensible and can be customized to meet specific filtering requirements. It integrates seamlessly with popular MTAs, making it a widely used choice for email filtering and content analysis in Linux server environments. Its modular architecture, extensive configuration options, and active community support make it a powerful tool for enhancing email security and reducing the impact of spam and malware.