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[IIS Tutor] Windows Server 2003 Internet mail solution- SMTP Part One

The Windows Server 2003 Internet mail solution consists of two components: the SMTP server,  and the POP3 server, which will be discussed in later articles.
SMTP that included in IIS  provides a way to create virtual e-mail servers that forward mail to designated
full-featured e-mail servers that provide client support (POP3, for example). In effect, the SMTP
service is primarily a message-forwarding service. Its advantage is that capacity to create multiple e-mail identities and servers to go along with each domain hosted on the server. The SMTP service can handle incoming mail from clients on the Internet or mail generated within a Web site.

After windows 2003 SP1 SMTP is not installed during the IIS 6.0 installation, you need to use add/remove Program to install SMTP, see Picture-1

Picture-1Installing SMTP Service

If you want  to create SMTP service,  select your machine in the left pane, right-click it, and select SMTP Virtual Server from the New menu. The New SMTP Virtual Server Wizard appears. To complete it, follow these steps:

Picture-2 Start SMTP Wizard
1. First, enter a friendly name that will be displayed in administrative tools to refer to this server. This generally should be the DNS name of the machine. Then, click Next.

Picture-3 Enter Name of SMTP Server
2. Next, select an IP address on which the SMTP server will listen, or specify All Unassigned to listen on all addresses configured on the machine. Click Next to continue.

Picture-4 Select IP address
3. Now, select the path to the directory where the SMTP server will store its files. IIS uses four directoriesBadmail, Drop, Pickup, and Queueto store mail, and on this screen you can specify where this cluster of directories will be stored. Click Next.
There will be four folders  created under server's home directory.
- Badmail. This folder stores undeliverable messages that can¡¯t be returned to the sender.
- Drop. This folder stores all incoming messages for domains handled by the virtual server.
- Pickup. This folder stores all outgoing messages. The SMTP service monitors the
Pickup folder, and as soon as a properly formatted message is placed in the folder, the
service collects the message and attempts delivery.
- Queue. This folder holds messages awaiting delivery. When a message can¡¯t be delivered
because of a communications failure or other problem, it leaves the message in
the Queue folder for later delivery attempts based on the settings configured for the
server (discussed later in this chapter).

Picture-5 Select Home Directory
4. Specify the default DNS domain that will be used for the SMTP server. Click Next when you're finished.

5. Review your choices, and click Finish to create the virtual server.
Now we have configured SMTP server, let's understand how the mail flows, Messages come to the server from the Internet, the LAN, or from an application on the server itself. These messages arrive
at the server through the virtual server¡¯s designated TCP port (25, by default); in the case of LAN or local messages, they are also placed directly in the Pickup folder. The SMTP service processes the message into the Queue folder and initiates delivery. It places the message in the Drop folder if the message is for a local recipient, or relays the message to the appropriate server if the message is for a remote recipient. Picture-6  illustrates the process.

Picture-6  SMTP processing incoming messages
For local recipients, delivery ends when the message is placed in the Drop folder. The process
for remote delivery is different. SMTP attempts to connect to the receiving mail server. If the
server can¡¯t be reached or a communications error occurs, SMTP places the message in the
queue for later delivery at intervals you designate for the server in its Delivery property page
(discussed later in this chapter). Once the receiving server acknowledges the message
receipt, SMTP removes the message from the Queue folder, indicating a completed delivery.

Note: SMTP supports Transport Layer Security (TLS) for remote delivery, providing enhanced security
by encrypting all outgoing messages. You can enable or disable TLS for individual remote
domains, giving you control over the remote domains for which SMTP uses TLS.

If you prefer, route outgoing messages from a virtual server to a smart host, which essentially
serves as an intermediary and takes care of transmitting the messages to their destinations.
The primary use of a smart host is to direct messages through a connection that might be
faster or less costly than the one the server otherwise uses for a direct delivery. A smart host
is specified in one of two ways: for the entire virtual server or for each remote domain hosted
on the server. The domain setting overrides the server setting, enabling you to route all outgoing
messages through a single smart host except for specific domains, which can be directed to
other smart hosts. Picture-7 illustrates the use of smart hosts for routing message delivery.

Picture-7 Smart hosts act as routing intermediaries.
SMTP offers support for several options that control security and connections for both
incoming and outgoing messages. For example, you can limit the number of connections for
both incoming and outgoing connections, specify timeout for connections, and limit the number
of connections per domain (outgoing). To secure both incoming and outgoing access,
SMTP supports anonymous authentication, basic (clear text) authentication against Windows
2000 and Windows Server 2003 domain accounts, TLS encrypted authentication, and
Windows Security Package (WSP)¡ªthe authentication mechanism built into Windows 2000
and Windows Server 2003. This last option enables clients to use the same single sign-on for
mail server authentication as for other enterprise resources, but it requires the use of an
e-mail client that supports WSP authentication. The version of Outlook Express included with

Windows 2000 and later supports WSP.

[IIS Tutor] Windows Server 2003 Internet mail solution- SMTP Part Two

[IIS Tutor] Windows Server 2003 Internet mail solution- SMTP Part Three