ESET MAIL SECURITY LINUX Installation Manual page 16

This chapter describes the integration of ESET Mail Security with a variety of known email
messaging systems. It is extremely important to understand the basic principles of an email
messaging system (see figure 5-1) and how ESET Mail Security integrates with it.
Figure 5-1. Scheme of UNIX OS email messaging system.
MTA - Mail Transport Agent
A program (e.g., sendmail, postfix, qmail, exim, etc.) that enables the transfer of email
messages between local and remote domains.
MDA - Mail Delivery Agent
A program (e.g., maildrop, procmail, deliver, local.mail, etc.) that enables the delivery of locally
addressed email messages into particular mailboxes.
MUA - Mail User Agent
A program (e.g., Microsoft Outlook, Mozilla Mail, Eudora, etc.) that provides access to and
management of email messages, such as reading, composing, printing, etc.
MAILBOX
A file or file structure on a disk serving as the storage space for email messages. Note that
there are several formats of MAILBOX in Linux/BSD/Solaris.
OS is an older format which stores email messages sequentially in a user-specific file in the
'/var/spool/mail' directory.
MBOX is a slightly newer but still outdated format which stores email messages sequentially
in one file located in the user's home directory.
MAILDIR stores email messages in separate files within a hierarchical directory structure.
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INTERNET
smtp
S1 MTA
S3
Email Server
smtp
User Agent
User Agent
Client Client
Local Network
smtp
S2
pipe
MDA
file
MAILBOX
S4
pop3/imap
User Agent
Client
ESET Mail Security