Postfix

Postfix is an SMTP mail transfer agent (MTA) used to send, receive, and route email between mail servers and local delivery services. Originally developed by Wietse Venema as an alternative to Sendmail, it is designed to be fast, secure, and straightforward to administer on Unix-like systems.

Key Features

• SMTP server and mail relay capabilities for inbound and outbound mail flow
• Queue management for reliable delivery and handling of transient failures
• Flexible routing and policy controls (transports, relaying rules, restrictions)
• Pluggable integrations for authentication, filtering, and content scanning via common mail workflows
• Support for modern operational needs such as TLS-encrypted SMTP and extensive logging

Use Cases

• Running an organization’s primary mail transfer agent for SMTP delivery
• Operating a secure outbound relay (smart host) for applications and servers
• Building a mail gateway in front of internal mailboxes with filtering and routing rules

Limitations and Considerations

• Postfix is an MTA, not a full groupware or webmail solution; mailbox access typically requires separate IMAP/POP and webmail components
• Advanced features (spam filtering, DKIM/DMARC, antivirus, mailbox storage) usually rely on integrating additional services

Postfix remains a widely deployed choice for SMTP delivery thanks to its security-focused design and mature operational tooling. It fits both small deployments and high-volume mail infrastructure when combined with appropriate mailbox and filtering components.