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|NetMail Technical White Paper
|NetMail Cool Solutions Article
|| from ratings
Posted: 8 Oct 2002
The intense need to communicate
and collaborate throughout the organization and beyond has made
e-mail a business-critical application. E-mail makes up the majority
of Internet usage today. An estimated 15 billion e-mail messages
were generated in the year 2000. According to the Aberdeen Group,
an independent market research firm, external e-mail between companies
is increasing at a rate of 100 to 150 percent a year.
Many organizations have already reaped substantial rewards by providing
their executives, managers, professional and specialty personnel,
and administrative support staff with e-mail, calendaring and other
collaboration tools. Now they are looking at ways to extend these
tools to the deskless workforce. This could literally double the
number of users that the information technology (IT) staff must
support because deskless workers represent more than 50 percent
of employees in the typical enterprise.1
Traditionally, implementing communication and collaboration tools
has been a major undertaking, particularly in environments with
a large user community. Supporting tens or perhaps even hundreds
of thousands of users has meant acquiring, deploying and maintaining
a number of high-end servers. User management in this environment
has been complex, cumbersome and time consuming. Many organizations
have multiple platforms-Linux*, Microsoft* Windows NT*/2000, NetWare®
and Solaris*. Many organizations have more than one e-mail and calendaring
system, further complicating the environment and placing an additional
burden on the IT staff. These factors have made it a difficult challenge
to deliver reliable service and acceptable performance to the user
community-especially in light of shrinking IT budgets and limited
Novell® NetMail™ provides a solution for organizations
facing these and other challenges associated with deploying e-mail
and calendaring tools to a large user base. Novell NetMail is a
scalable, high-performance, standards-based messaging solution that
provides e-mail, calendaring and scheduling across the Internet.
It offers a high level of scalability-with proven support for 210,000
users on a single server. It can run on a single server or distributed
across multiple servers to ensure scalability, reliability and high
performance. It supports the leading e-mail, calendaring, Internet
and security standards, and it runs on multiple platforms-ensuring
flexibility and eliminating concerns about being locked into a single-vendor
Novell also offers Novell NetMail XE, a simple and cost effective
e-mail solution for small organizations that run Microsoft Windows*
primarily. NetMail XE is reliable and easy to implement, and it
supports standard Post Office Protocol (POP) and Internet Messaging
Access Protocol (IMAP) clients, including Microsoft Outlook* and
Netscape*. There is no need to install a directory or deal with
the complexities of integrating Active Directory* and Exchange.
NetMail XE leverages the Windows user registry and automatically
enables existing users for Internet e-mail. For more information
on NetMail XE, see the Novell NetMail XE Implementation Guide.
You'll find it at: http://www.novell.com/info/collateral/docs/4621305.01/4621305.html
This paper provides a description of NetMail XE software, including
an overview of its architecture, a detailed description of the agents
that comprise the system, and a discussion of deployment on single-
and multiple-server installations.
Source: AmeriStat (Population Reference Bureau) 2000.
||Overview Of The NetMail
Novell NetMail is a scalable, high-performance
e-mail and calendaring system that is based on Internet-standard
messaging, calendaring and security protocols. NetMail is built
on Novell eDirectory™, which has proven itself in more than
ten years of operation and is now in use by more than 420 million
users worldwide. eDirectory permits nearly limitless scalability
and has been tested with more than one billion objects in a single
NetMail supports full eDirectory functionality, including NDS®
(Novell Directory Services®) User and Group objects, NDS aliases
(for login and addressing) and NDS organizational roles. Through
NDS User objects functions, NetMail provides:
- Immediate effectiveness of changes in user-specific information
(for example, forwarding configuration or quota changes).
- Disabling or temporary suspension of NetMail functionality
for NDS User objects.
- Automatic creation of mailboxes for NDS User objects when an
account is first accessed through a NetMail agent.
With NetMail, organizations enjoy the advantages that come with:
- Extensive scalability
- Single-point management
- Support for multiple access devices
- Support for popular e-mail, calendaring, Internet and security
- Ability to extend functionality
- Secure transport
- Platform independence
- Extensive monitoring, logging and reporting
NetMail scales to fit virtually any size environment, from 10 users
to hundreds of thousands of users. Consequently, it meets the needs
of many organization types, including large enterprises that want
to expand e-mail and calendaring to deskless workers, Internet service
providers (ISPs), application service providers (ASPs), institutes
of higher education, school systems, government entities, and small
and midsize businesses.
The multithreaded, multiprocessor NetMail architecture takes full
advantage of available server hardware to achieve optimum performance.
In a recent SPECmail2001 2
benchmark test, NetMail processed 1,050 SPECmail2001messages per
minute-the equivalent of supporting 210,000 users-all on a single
IBM* eServer xSeries 342.
Rather than simply throwing high-end server hardware at the SPECmail2001
test to ensure good results, Novell and IBM set out to determine
how to optimize NetMail to best utilize the power of a single cost-effective
server, such as the IBM eServer X342. The test was run using off-the-shelf
hardware and software. Test team members combined their expertise
to tune the NetMail system for the IBM server using standard NetWare
tuning parameters. (No special software or patches were employed.)
The benchmark results are available at the SPECmail Web site at
www.spec.org. The results provide
details on the NetWare parameter settings used to support this large
number of users. NetMail customers can use this information to save
time and money in tuning the NetMail system for their environments.
Administrators can manage NetMail user accounts, hardware and software
configuration, and security all from a single point through eDirectory.
They have a global view of user accounts, which simplifies user
setup, administration and support. NetMail offers two administrator
interfaces: NetWare Administrator (NWAdmin) and WebAdmin. Administrators
who are familiar with NWAdmin can maintain and configure the system
using the NWAdmin snap-in that is included with NetMail. The snap-in
allows the administrator to create and modify NetMail objects from
Administrators who prefer to perform administrative tasks through
the Web can use WebAdmin, a browser-based interface that enables
any time, anywhere Web-based access. With WebAdmin, all activities
can be performed via SSL (Secure Sockets Layer) connections. SSL
support makes it possible to maintain a NetMail system remotely
and securely over the Internet.
Support for a variety of access devices
NetMail supports all browser-based access devices. Consequently,
users can access their e-mail messages and calendars using whichever
access device they prefer-a desktop or laptop computer, cellular
phone, personal digital assistant (PDA), or even an Internet kiosk.
NetMail also enables Palm OS* and Pocket PC* synchronization of
e-mail, calendar and address book data from any network workstation
containing the synchronization software and docking device. This
extensive device support empowers the organization to extend its
network to encompass all types of employees, from traditionally
connected knowledge workers to deskless workers, and from employees
who work from a fixed location to those who are highly mobile.
Support for popular industry standards
NetMail supports all popular e-mail, calendaring, Internet and
security standards, including:
- Network Messaging Application Protocol (NMAP). A text-based
IP protocol registered with the Internet Assigned Numbers Authority
(IANA) at port 689. NMAP support permits NetMail agents to be
distributed across multiple servers and use NMAP to communicate.
- Post Office Protocol Version 3 (POP3) and Internet Message
Access Protocol Version 4 (IMAP4). Ensures compatibility with
Novell GroupWise®, Microsoft Outlook and Outlook Express,
Microsoft Exchange, Netscape Communicator, Eudora*, Pine, Pegasus
Mail and other integrated and standalone e-mail clients.
- Simple Mail Transfer Protocol (SMTP). Ensures compatibility
with e-mail servers on the Internet and most TCP/IP systems.
- Lightweight Directory Access Protocol (LDAP). Enables
NetMail to perform lookups
in eDirectory, Netscape Directory Server*, Microsoft Active Directory*
or one of the many Web-based address books to locate organizations,
individuals or any other resource within that directory.
- HyperText Transfer Protocol (HTTP). Permits users to
access their mailboxes from any standard Web browser. Also permits
system administrators to manage NetMail user accounts and messaging
configurations from any standard Web browser.
- Security standards. Supports SSL 3.0 on all protocols,
including POP3, IMAP4, SMTP and HTTP. Also supports the OpenSSL
implementation of Transport Layer Security (TLS) in the SMTP agent,
and Secure Multipurpose Internet Mail Extensions (S/MIME).
- iCalendar protocol. Provides a common format for openly
exchanging calendaring and scheduling information across the Internet.
Permits NetMail calendaring functions such as calendar events,
tasks and notes to be used in conjunction with any other iCal-compliant
- Wireless Access Protocol (WAP) and Wireless Markup Language
(WML) support. Provides support for wireless devices that
are compatible with the WAP and WML standards. Enables mobile
phone users who have a WAP/WML-enabled phone to access and manage
their e-mail via a mobile phone-keeping in touch even when they
don't have access to a computer.
Table 1 lists some of the many standards that NetMail supports.
Table 1. NetMail standards support.
||Simple Mail Transfer Protocol
||ARPA Message Format
||Requirements for Internet Hosts
||Simple Network Management Protocol
||SNMP Management Information Base
||SNMP Trap Conventions
||8-bit SMTP Transport
||Vietnamese Character Message
||Modular Web Agent
||Japanese Character Message Encoding
||Modular Web Agent
||Lightweight Directory Access
||Address Book Agent
||SMTP Extension Syntax
||SMTP Size Extension
||SMTP Delivery Status Notifications
||Chinese Character Message Encoding
||Post Office Protocol Version
||SMTP Remote Message Queue Starting
||Multipurpose Internet Mail Extensions
||MIME Part II
||MIME Part III
||Internet Message Access Protocol
||POP3/IMAP4 Authentication Command
||SMTP Command Pipelining SMTP
||MIME Charsets, Languages, and
||Transport Layer Security (TLS)
||SMTP, POP, IMAP, Modular Web,
||Unicode* Transformation Format
||Modular Web Agent
||Secure Sockets Layer (SSL)
||SMTP, POP, IMAP Agents
||POP3 Extensions Mechanism
||Secure Sockets Layer (SSL)
||SMTP, POP, IMAP, Modular Web,
||Public Key Cryptography Standards
||SMTP, POP, IMAP, Modular Web,
||SMTP, POP, IMAP, Modular Web,
||Internet Calendaring and Scheduling
Core Objects Specifications (iCalendar)
||ModWeb Calendar Module
||iCalendar Message-Based Interoperability
||ModWeb Calendar Module
Novell has extended the functionality of NetMail beyond the services
provided by SMTP, POP3 and IMAP4 protocols. Extended services include
anti-spam, aliasing, autoreply, forwarding, LDAP, anti-virus, rules
and calendaring services. Other custom services can be added using
the IP-based NMAP protocol and other interfaces.
NetMail provides secure transport, permitting users easy access
to mail over the Internet while ensuring privacy and protection
of confidential information.
NetMail runs on all popular platforms including Linux, NetWare,
Solaris and Windows XP/2000/NT. As a result, organizations can take
advantage of the power of NetMail without introducing new platforms
that might complicate the IT environment.
Extensive monitoring, logging and reporting
NetMail provides extensive monitoring, logging and real-time statistics
reporting. NetMail also monitors the messaging server's performance.
These capabilities enable administrators to stay on top of system
operation and performance to ensure high quality of service for
by the Standard Performance Evaluation Corporation (SPEC), SPECmail2001
is the first standardized benchmark that measures mail-server performance
using a real-world workload. Details on the SPECmail benchmark results,
are available at: http://www.spec.org/osg/mail2001/results/res2002q1/mail2001-20020312-00014.html
NetMail is built on a modular architecture
that offers extensive flexibility without compromising system integrity.
Product functions are strategically divided among several components,
so an organization can install only those components it requires.
Moreover, the components can be located on a single server or distributed
across multiple servers based on usage and system resources.
NetMail components include:
- Messaging Server(s). Any server on the network that hosts
one or more NetMail agents. The building-block architecture enables
the organization to implement its entire messaging system on a
single server or distribute it across multiple servers for higher
reliability, faster performance and greater scalability.
- eDirectory. NetMail leverages existing eDirectory objects
by adding NetMail-specific attributes to these existing objects.
It also creates new NetMail-specific objects.
- NetMail agents. A series of executables that perform
specific product functions. NetMail agents can all be run on the
same server or distributed across multiple servers.
Tight integration with eDirectory
NetMail integrates tightly with eDirectory. It adds NetMail specific
attributes to existing eDirectory components such as server objects,
container objects and user objects. It also adds NetMail specific
- Internet Services container
- Messaging Server object
- Parent objects
- Mailing Lists
NetMail uses eDirectory exclusively to store and look up user information
and system configuration parameters. The only items that NetMail
does not store in the directory are the e-mail messages themselves.
During the initial NetMail installation, the installation program
extends the eDirectory schema to include NetMail related objects
and attributes. Existing NDS objects, such as Container and User
objects, take on new NetMail attributes.
Internet services container
Because it is part of NetMail, the Internet Services container
differs from other NDS container objects. There can be only one
Internet Services container per tree and, as the messaging system
container, it contains only NetMail component objects.
Messaging server object
When NetMail is first installed, the install program automatically
creates a Messaging Server object in the Internet Services container
to represent the physical server on which the NetMail software is
installed. The Messaging Server object is represented as a container
with server attributes. It sets the messaging server properties
and it "contains" all NetMail agents running on that
The install program automatically creates a Parent Objects container
in the Internet Services container to provide a centralized location
for Parent objects. NetMail permits the administrator to create
Parent objects allow administrators to manage agent services and
user settings collectively for specific sets of users. This enables
the administrator to subdivide a single messaging system into configuration
subunits. For example, by creating separate Parent objects for each
domain, administrators can manage every domain as if it were a separate
The configuration options in the Parent object allow administrators
to grant access to messaging services selectively. The administrator
can enable or disable different agent services for each Parent object.
For example, in an ISP environment, the system administrator could
use Parent objects to give one hosted domain access to POP, 5 MB
mailbox quotas and Spanish as the default language. The administrator
could give another domain access to IMAP in addition to POP, with
10 MB mailbox quotas and a default language of German. This permits
the ISP to bill for individual services and increased storage. Agents
running on both distributed and standalone messaging servers dynamically
look up the user's Parent object in the tree to determine what rights
the user has to the service provided by the agent.
Parent objects can also be used to distribute administrative tasks,
giving certain individuals the right to create, delete, modify or
import user accounts in specific Internet domains. For example,
in a corporate environment, the system administrator could use Parent
objects to permit administrative assistants to create user accounts
for their respective departments.
NetMail agents are a series of executables
that perform specific product functions. The agents have plug-and-play
versatility, that is, they can be combined in a variety of configurations
and still maintain the functionality of a single, integrated messaging
system. Table 2 provides a list of NetMail agents.
Table 2. NetMail agents.
||Mail Proxy Agent
|Modular Web Agent
|Address Book Agent
||List Server Agent
The NMAP Agent is the heart of the NetMail system. It is responsible
for message processing and delivery as well as for the physical
mailboxes and message queues. The NMAP Agent:
- Provides mailbox access to other agents.
- Moves messages through the queuing system.
- Notifies other agents when they need to take action on a message.
- Enforces disk quotas (configurable globally or at the user
- Maintains only a single copy of a message sent to multiple
users to conserve disk space.
NMAP acts as a traffic cop for messages, from the time a message
enters the message queue until it is delivered to the user's mailbox
or passed off for delivery via the Internet. The NMAP Agent determines
what other agents need to process a message and in what order. To
ensure fast performance and high scalability, the NMAP Agent is
multithreaded and can simultaneously process as many messages as
NMAP is the only NetMail agent that performs file access. All other
NetMail agents gain access to mailboxes and message queues through
the NMAP Agent using the NMAP protocol.
Because it is core to NetMail, all NetMail systems must have at
least one NMAP Agent. Additional NMAP Agents can be added to any
server in the directory tree. This is typically done to distribute
mailboxes over multiple servers or to move mailboxes closer to remote
The NMAP Agent also permits control of bounced messages to prevent
spammers from using bounced messages to disguise spam. Spammers
sometimes falsify the From: field in their message so the
resulting bounced messages go to a mail server other than their
own. As a result, the server that owns the domain specified in the
From: field is inundated with thousands of bounced messages
in a short period of time.
The NMAP Agent permits the administrator to set a threshold for
the number of bounced messages it will process within a set time
period. If the number of bounced messages exceeds the defined threshold,
the messages are deleted instead of being processed.
The SMTP Agent is responsible for receiving mail and sending mail
to remote mail systems over the Internet. This agent can also be
used by standards-based mail clients to drop off messages.
The SMTP Agent streams incoming messages to the NMAP Agent, and
the NMAP Agent notifies the SMTP Agent when queued messages are
ready to be sent to remote systems. (A single SMTP Agent can be
used to pick up outbound messages from multiple NMAP Agents.)
The SMTP Agent supports Extended SMTP (ESMTP) and SMTP-after-POP
authentication. In ESMTP authentication, the e-mail client must
authenticate through SMTP-Auth before the SMTP Agent will relay
its messages to remote recipients. In SMTP-after-POP authentication,
users cannot send remote messages through the SMTP Agent until they
have first authenticated with the messaging system via their POP3
or IMAP4 client.
NetMail SMTP Agent has several features for preventing unsolicited
bulk e-mail (spam or UBE). It can be set up to refuse incoming messages
from IP addresses that are:
- In the ranges configured by the administrator.
- Listed in the Realtime Blackhole List (see http://maps.vix.com/)
or other similar services such as ORBS, Spamcop and SPEWS.
- Not resolvable via Domain Naming Services (DNS).
The SMTP Agent can also be set up to relay messages only if:
- The sender's IP address is on a list configured by the administrator.
- The sender has authenticated through SMTP-Auth.
- The sender has recently authenticated through POP3 or IMAP4
The SMTP Agent supports multiple
Internet domains on a single messaging system. This capability permits
hosted domains to have separate address books and separate message
stores-a feature that is especially important for service providers.
POP3 and IMAP4 Agents
The POP3 and IMAP4 Agents provide support for GroupWise, Microsoft
Outlook and Outlook Express, Microsoft Exchange, Netscape Communicator*,
Eudora, Pine, Pegasus Mail and other integrated and standalone e-mail
clients. This gives people the flexibility to use any e-mail clients
they choose-even keeping their current e-mail clients if they wish.
Modular Web Agent
The Modular Web Agent provides the browser-based interface to the
NetMail mailbox and calendar. It is customizable to provide maximum
flexibility to users and administrators. Two HTML client interfaces
are included with NetMail: WebMail and WebAccess. NetMail also includes
the tools for creating additional HTML interfaces.
The WebMail interface is patterned after the Novell Internet Messaging System (NIMS) 2.5 mail client interface. The WebMail client provides standard mail client functionality, including:
- Reading and sending messages.
- Attachment support (sending and receiving).
- Personal address book.
- LDAP address lookup.
- Mailbox folder management.
- Quota monitoring.
- Support for single- and double-byte language encoding.
- User interface in multiple languages.
Additionally, administrators can give users access to self-administration
features through the WebMail interface. Self-administration features
- Changing the user's eDirectory password (the NetMail and eDirectory
password are the same).
- User interface configuration (colors, character sets and other
- Configuration of automatic message forwarding and custom message
- Proxy configuration to pull messages from other accounts.
The WebAccess interface provides all the features of WebMail plus:
- Integrated help.
- A calendar capability that permits users to maintain a calendar
of appointments, create and accept appointments, maintain notes
and manage tasks.
- A delegation capability that permits administrators to use
the WebAccess interface to give selected users access to NetMail
administrative functions such as adding, modifying and deleting
The Modular Web Agent includes several submodules that enable various
- IMS Mail Module provides mail and address book functions.
- IMS Calendar Module enables the WebAccess calendar features
including appointments, tasks and notes.
- IMS Preferences Module allows users to set or change preferences
using Preferences in the WebMail template, or the Options screen
in the WebAccess template. Settings include:
- Reply-to address
- Default character set
- Preferred language
- Web template
- IMS Task Management Module enables delegation of administrative
functions such as creating, modifying or deleting users.
Because the administrator can modify the user interface templates,
the administrator has substantial control over what users can and
cannot see and do through the user interface. As a result, the administrator
can limit the scope of users' access to Modular Web Agent services.
The Calendar Agent provides automatic status tracking information
for scheduled appointments, tasks and notes. When a user schedules
a calendar event, the Calendar Agent processes all Accept and Decline
responses and automatically updates the event's status information
in the event organizer's calendar. If the administrator chooses
not to run the Calendar Agent, users receive
iCal status messages in their inbox.
Address Book Agent
The Address Book Agent provides an LDAP server for resolving address
lookups against eDirectory. The agent runs lookups against eDirectory,
searching for users matching the LDAP search criteria. Information
returned about each user depends on the user's privacy level that
is set in Preferences/Options.
The Address Book Agent answers requests at a high rate. To speed
LDAP queries, the agent maintains an index of all users in its supported
NDS contexts, making it possible to use the agent with the address
type-ahead feature of many popular e-mail clients.
The agent can also be configured to automatically create a publicly
accessible LDAP Data Interchange Format (LDIF) file of all user
information (except for information or accounts protected by NetMail
The Forwarding/AutoReply Agent permits automatic reply to all incoming
e-mail. It also permits e-mail to be forwarded automatically to
other e-mail addresses. A user may specify a custom auto-reply message
that is returned to senders of all incoming e-mail, and one or more
addresses to which messages are to be automatically forwarded. For
example, the forwarding feature permits the delivery of Short Message
Service (SMS) messages to cellular phones and pagers while at the
same time delivering the messages to a user's mailbox.
The Forwarding/AutoReply Agent is independent of any e-mail client.
Although users configure mail forwarding and autoreply messages
using the Modular Web client, the agent functions independently
of any e-mail client, including the Modular Web client. That's because
each user's forward and autoreply information is stored in the NDS
User Object. As a result, NetMail can handle forwarding and autoreply
messages for users of POP3, IMAP4 and Modular Web clients independently
of the clients.
The Rule Agent executes rules defined in the Modular Web Agent.
Rules can be defined for moving, copying, deleting or forwarding
mail based on From:, To:, CC:, Subject or Body. For example, a rule
can specify that all messages containing "Marketing"
in the subject and are from "jjones" are to be moved
to the "Marketing Review" folder.
Like the Forwarding/AutoReply Agent, the Rule Agent is independent
of any e-mail client. Although users configure rules using the Modular
Web client, the agent functions independently of any e-mail client,
including the Modular Web client. That's because user's rules are
stored in the NDS User object. As a result, NetMail executes the
configured rules whether the user opens messages in a POP3, IMAP4
or Modular Web client.
Mail Proxy Agent
The Mail Proxy Agent permits users to configure their accounts
to consolidate messages from up to three external POP3 or IMAP4
messaging systems into their NetMail mailbox. Either the administrator
or the user can set user preferences to configure which hosts/accounts
the Mail Proxy Agent accesses.
Unlike some messaging systems in which messages are received as
attachments, the Mail Proxy Agent places messages in the NetMail
mailbox with no change to the header. Consequently, the NetMail
mailbox appears as the final destination.
In addition to consolidating messages into a single mailbox for
the convenience of the user, the Proxy Agent can also facilitate
the transition from an old messaging system to NetMail.
The Alias Agent allows a network administrator to configure one
or more user aliases for a single NDS User object. If configured
to do so, NetMail pulls the user account information directly from
eDirectory and generates the aliases automatically.
For example, when setting up the system, the administrator can
use the Alias Agent to generate names in the form FirstName.LastName.
To the outside world, e-mail addresses for users within the organization
appear as FirstName.LastName@YourDomain.com. (Of course, NDSLogin@YourDomain.com
is also a valid address.) With aliasing, users still authenticate
to the messaging system using their regular NDS login names, so
there is no confusion to users, and the administrator does not have
to create an alias manually for every user.
The formats automatically provided by the Aliasing Agent are:
- FirstName_LastName@domain.com (firstname.lastname@example.org)
- FirstInitialLastName@domain.com (email@example.com) (This format
is limited to eight characters before the "@".)
- FirstName.LastName@domain.com (firstname.lastname@example.org)
- FirstName.MI.LastName@domain.com (email@example.com)
- FirstName_MI_LastName@domain.com (firstname.lastname@example.org)
An administrator may also create custom e-mail aliases. For example,
email@example.com can be set as an alias of any particular NDS
User or supported object.
The Anti-virus Agent integrates with McAfee NetShield*, Computer
Associates InoculateIT/eTrust* and Symantec CarrierScan* (also known
as Symantec Scan Engine 3.0) virus engines to provide virus scanning
on all messages handled by NetMail. All messages are scanned regardless
of whether they originate from external addresses or are internal
messages that never leave the NetMail system.
The Anti-spam Agent allows the Postmaster or NetMail administrator
to create a blackout list of undesirable e-mail domains and addresses.
NetMail does not accept messages sent from domains and e-mail addresses
contained in the blackout list.
List Server Agent
The List Server Agent provides List Server functionality in a NetMail
environment. It supports a range of functions, from two-way, fully
interactive discussions to one-way lists that deliver announcements,
newsletters and advertising without allowing responses. Typically,
users subscribe to list server mailing lists via e-mail.
The List Server Agent works in conjunction with NDS Mailing Lists
and standard e-mail Mailing Lists. NDS based mailing lists are built
from NDS Container, Group or User objects. Standard mailing lists
are e-mail based and require the full e-mail address of each subscriber.
The Connection Manager keeps track of authenticated users. When
a user logs in via POP3 or IMAP4, the POP or IMAP Agent grabs the
client's IP address and sends it to the Connection Manager Agent.
The Connection Manager Agent then keeps track of the IP address
for a designated time period (the default is 15 minutes). NetMail
considers a user to be authenticated for as long as the Connection
Manager maintains his or her IP address.
||Distributing NetMail Across
Like traditional e-mail systems,
NetMail can run on a single server-with all agents running on the
same server. NetMail has demonstrated its ability to support up
to 210,000 users on a single server.
In addition, and unlike traditional e-mail systems, NetMail is
not limited to an environment in which all messaging system services
must run on the same server. NetMail agents can operate across multiple
servers, and communicate using the NMAP protocol. When combined
with the distributed nature of Novell eDirectory, the NMAP protocol
allows NetMail agents running on different servers (even on different
platforms) to operate as if they were on the same server.
Because it can operate in both a single server and a distributed
environment, NetMail offers considerable flexibility in configuration.
This is the simplest NetMail configuration because the NetMail
messaging server is the only server in the NDS tree. All NetMail
components are installed on the same server (see Figure 1).
This configuration is typically implemented by small to medium organizations
in which NDS is not used for other network services.
Single messaging server LAN
In this configuration, more than one server exists in the NDS tree,
but only one server is needed to provide messaging services (see
Figure 2, previous page). This configuration is typically implemented
by small to medium size organizations in which NDS is also used
for other network services
Multiple standalone messaging server LAN
Multiple single-server, standalone systems can be run on the same
network (see Figure 3). Each messaging server is assigned
to a different domain and functions as an independent messaging
system. This configuration is typically used in medium to large
enterprises that have several separately managed information technology
(IT) departments and Internet domains or subdomains
Multiple distributed messaging server LAN
This configuration implements a messaging system in which message
traffic exceeds the resources of a single server, but all messaging
servers share the same high-speed network (see Figure 4).
This configuration is typically used in ISP, ASP, or medium to large
enterprise LAN environments.
Multiple messaging server WAN
This configuration consists of a network in which the messaging
system connects different geographical locations, but users still
receive messages at the same Internet domain (see Figure 5).
This configuration is typically implemented in government and enterprise
organizations that have one or more remote locations.
Building fault tolerance
An organization can optionally increase NetMail fault tolerance
by implementing redundancy and failover support at either or both
of two levels: the application level and the hardware level.
Application-level clustering consists of duplicating critical mail
services on multiple servers. Because of the highly modular NetMail
architecture and eDirectory replication, critical services can be
run simultaneously on multiple servers, each providing the same
service to users. If one server fails, alternate servers continue
to provide services to users for continuous availability. This provides
fault tolerance for most mail services at the application level.
The only NetMail component that cannot be cloned at the application
level is the message store.
With hardware-level clustering, servers are connected in a group.
If a server in the group fails, automatic failover to another server
in the group occurs. Consequently, operation continues with little
or no disruption to users.
For example, only one NMAP Agent should be deployed to service
a given user context and its associated mailboxes, yet NMAP is a
critical service and needs to be protected against server failure.
Hardware level clustering allows the NMAP service to failover to
another server so users can still retrieve their mail in the event
of a server failure.
Advantages of a distributed NetMail system
Organizations can gain several important advantages by distributing
NetMail across servers. These advantages include:
- Increased fault tolerance for higher reliability. Service
redundancy and failover support can be implemented at the application
level and at the hardware level to shield critical processes from
a single point of failure.
- Faster performance for increased user satisfaction. The
organization can provide round-robin DNS entries for redundant
servers to distribute the workload evenly across servers. Distributing
the workload in this way results in faster performance.
- Greater scalability to support a growing number of users
and an expanding message volume. An organization can start
with a single server installation and migrate to a distributed
environment as workload increases. Instead of replacing a server
with a bigger server, the IT staff simply adds servers. There
is no need to reinstall the system, and NetMail maintains all
configuration information. As a result, the migration to a distributed
environment is simple, straightforward and non-disruptive.
Supported by licensing and platform flexibility
NetMail is licensed on a per-mailbox basis rather than on a CPU
or platform basis. As a result, when moving from single to distributed
mode the organization need not purchase additional licenses or copies
of NetMail, as long as the total number of licensed mailboxes is
There is no need to purchase separate NetMail versions for different
operating systems. NetMail ships with versions for all supported
operating systems on a single distribution medium. As a result,
the organization can configure NetMail in a mixed environment as
a single, distributed system. For example, the organization can
run some agents on NetWare and others on Linux, Solaris and Windows-without
Attractive in large message environments
Distributed message servers are most often used in larger message
systems such as those run by ISPs, ASPs and enterprises with multi-LAN
environments. Because of message traffic volume, performance requirements
or the local distribution of the network, these organizations typically
require multiple messaging servers to provide the load balancing,
fault tolerance and speed required to service their customers. The
ability to operate across multiple servers and platforms makes NetMail
an excellent choice for these organizations.
IT professionals are under pressure
to provide e-mail and calendaring services to a rapidly expanding
number of users. Supporting a large user base and a growing message
volume has required considerable time, effort and money. Traditional
e-mail and calendaring systems require the deployment of a large
number of servers to support the thousands of users that many organizations
have to service. Moreover, traditional systems don't offer
the scalability, reliability, performance or affordability that
large enterprises, colleges and universities, school systems, ASPs
and ISPs, and other organizations need to ensure the availability
of these essential tools to their users.
With its directory foundation and advanced architecture, Novell
NetMail can support hundreds of thousands of users on a single server
without sacrificing performance. What's more, NetMail can
be distributed across multiple servers to ensure continuous availability
and a high level of scalability.
With NetMail, organizations can extend e-mail and calendaring across
the enterprise and beyond, while simplifying management, minimizing
support requirements and reducing costs.
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