Chapter 1. About the Volution Messaging Server

Caldera Volution Messaging Server is a messaging server product built around directory services and industry-standard open source components. The design goals of the Messaging Server required:

The principle components of the Messaging Server are:

OpenLDAP (directory services)
  

The Messaging Server uses a Lightweight Directory Access Protocol (LDAP) directory to store information concerning mail accounts, mail aliases, and the mail domains configured on your server. OpenLDAP is the directory server for the Messaging Server. Both personal and corporate user information and mail authentication are all stored in the directory and now easily managed using the Server Manager.

Postfix (MTA) 

The heart of any messaging server is the Mail Transfer Agent (MTA), which is responsible for queuing and routing of email messages, handling mailing lists and aliases, and forwarding email. Postfix is the Mail Transport Agent for the Messaging Server. Unlike other MTA systems before it, Postfix (originally known as IBM Secure Mailer) was designed explicitly with security in mind. Postfix has been configured to query the LDAP directory for information needed to deliver mail to the correct Cyrus inbox and to resolve mail aliases.

Cyrus (message store)
  

The message store is used to store mail folders. The Cyrus message store provides access to personal mail through the Internet Message Access Protocol (IMAP4) and Post Office Protocol (POP) via its IMAP and POP server. IMAP and POP servers are key components that allow email clients to connect to the server and fetch mail. The Cyrus server differs from other message store and IMAP server implementations in that it is run on "sealed" servers, where users are not normally permitted to log in. The Cyrus server queries the LDAP directory for authentication of users using the pam_ldap interface on Caldera OpenLinux.

The Cyrus message store is stored in parts of the filesystem that are private to the Cyrus system and all user access to mail is only through clients using the IMAP and POP3 protocols. This means that Messaging Server mailboxes are not compatible with traditional UNIX or Linux flat file mailbox format and you will not be able to access them using mailx or any other client that does not support IMAP or POP. However, the Cyrus database mailbox format provides a message store which is much more scalable than the traditional flat file format. Also, users are able to access their mail from command line utilities, but they will have to use the fetchmail utility to do so.

The Messaging Server also provides:

PAM LDAP module 

The LDAP Pluggable Authentication Module provides the ability for IMAP and POP services to authenticate against passwords stored in the LDAP directory.

OpenSSL 

OpenSSL is a Secure Sockets Layer communications library that provides cryptographic security for the Cyrus IMAP and POP servers and the Server Manager interface.

Apache -- webserver 

The Messaging Server configures the standard Apache webserver (installed by default with Caldera OpenLinux) to serve the Server Manager mail administration and mail client preferences interfaces.

MUA support 

An email client is called a Mail User Agent (MUA). MUA functionality is often included with Internet browsers together with calendar clients capability. The Messaging Server supports standard mail clients, and it provides a user management interface to enable server-based functionality on Outlook clients.

local delivery agent 

MTA's do not communicate directly with the message store, rather they call a local delivery agent, which is a simple program that knows how to place a mail message in a given user's inbox. The local delivery agent for the Messaging Server is the Cyrus deliver program.