1 Software and Local Network Environment

This document describes the configuration of mail services on a Fedora (FC3 or FC4) machine serving a small research network of Windows, Mac, and Linux boxes. The system is probably “over engineered” for its actual use case but may prove interesting in other environments. The main components include:

  • Postfix (2.2.2) as the mail transfer agent.

  • Amavisd-new (2.3.1) as a SMTP proxy for spam filtering and anti-virus scanning.

  • SpamAssassin (3.0.3) as the spam filtering agent.

  • Razor Agent (2.67) as a supplemental spam filter.

  • ClamAV (0.85) as the anti-virus scanner.

  • Cyrus IMAP (2.2.12) as the mail store.

  • Cyrus SASL (2.1.20) acts as the mail store’s authentication agent.

The IMAP mail store also resides on this machine. Port 25 is open to the internet for SMTP traffic. Inbound mail is routed as shown in Figure 1.

Figure 1: Inbound Mail Routing Diagram

Network Environment. The local network is isolated behind a NAT router. It is assigned a private domain name (e.g. internal.lan). The mail host is physically located on the local network (e.g. mail.internal.lan). A public domain name (e.g. external.com) is mapped to the router’s IP address by a commercial DNS registration service. All local network users are provided with virtual mail boxes in the public domain’s name space (e.g. user@external.com). All virtual mail boxes are housed in the IMAP mail store. Deliveries to local accounts on the mail host are also routed to the IMAP store.

Software Availability. The system is built from off the shelf RPM’s. An attempt is made to stay as “close to the source” as possible. Hence, the preferred repositories are Fedora and Fedora Extras. Other “reputable” sources are used as needed. Currently, the following packages are used: