Page 6 - Mercury Manual.book

1 Overview of Mercury/32
Introduction

Overview of Mercury/32

Introduction

Mercury/32 is a Mail Transport System — a suite of programs designed to move electronic
mail messages from one computer system to another (possibly different) system. Unlike a
user agent, or client such as Pegasus Mail, with which individual users interact to read and
send mail, Mercury is seldom directly encountered by users; its operation is largely invisible
— it is a “black box” running in the background, performing tasks autonomously.

Mercury/32 is divided into a core processing module (MERCURY.EXE) and a set of “service” You can change the set
components, called protocol modules. Each protocol module supplies a specific service to the of protocol modules Mer-
core processing module – for instance, the Mercury SMTP Server Module, MERCURYS, ac- cury loads at any time us-
ing the Protocol Modules
cepts incoming mail delivery connections and submits them to the core module for process- option on the Configura-
ing. The core module is responsible for routing mail (that is, deciding whether messages are tion menu.
local or need to be sent to the outside world), and for providing core services such as the au-
tonomous mail server, mailing list management and error handling.

The following protocol modules are supplied with Mercury/32:

MercuryS – SMTP server module This module is responsible for handling incoming mail de-
livery connections from the outside world. It accepts mail and places it in the core module’s
mail queue for processing. MercuryS implements the Internet SMTP standard (Simple Mail
Transfer Protocol) and supports several Extended SMTP extensions.

MercuryC – SMTP client module MercuryC is responsible for sending mail to the outside
world using the Internet SMTP mail protocol. MercuryC is what is known as a relay mailer
– it does not attempt to deliver mail directly to the recipient; instead, it asks a larger SMTP
implementation (often a unix host) to deliver it on its behalf. This relay model makes Mercu-
ryC particularly suitable for use behind firewalls, since it can ask the firewall system to send
mail on its behalf.

MercuryE — SMTP direct delivery module MercuryE is an alternative SMTP client module
for Mercury; like the MercuryC module, it is responsible for sending mail from your system
to the outside world. Unlike MercuryC, though, MercuryE can perform complete end-to-end
delivery without requiring a relay host. MercuryE is typically used in situations where you
have either a permanent Internet connection, or one with fast establishment, such as an ISDN
connection. You can choose to install either MercuryC or MercuryE, depending on your
needs, but you can only install one, not both.

MercuryP – POP3 server module MercuryP listens for connections from POP3 client pack-
ages, such as Pegasus Mail, Eudora or Outlook Express, and provides access to new mail
waiting on the server via the POP3 protocol. MercuryP conforms to Internet Standards Doc-
ument RFC1939, including support for advanced commands such as APOP and UIDL.

MercuryD – POP3 client module MercuryD acts as a POP3 client on behalf of one or more
users on your system. Using MercuryD to download mail for your users from an Internet
Service Provider allows you to centralize your Internet connection to the single machine
where Mercury runs – users can see their mail without their own workstations actually being
connected to the Internet or having modems. MercuryD can also retrieve mail from Domain
Mailboxes – that is, single mailboxes where all mail destined for a specific domain gets de-
livered – and route the contents to the local users on your system.