CHAPTER 22

MICROSOFT OUTLOOK WEB ACCESS

Microsoft Outlook Web Access (OWA) has evolved from an Active Server Page (ASP)-based

programming sample to a serious messaging and collaboration client based on the Internet Server

Application Programming Interface (ISAPI).

Lesson 1: Outlook Web Access Overview

OWA supports e-mail, calendar features, and contact management, which represent essential

information management features.

Outlook Web Access Architecture

OWA requires Microsoft Windows 2000 Server and Internet Information Service (IIS) 5.0.

Based on a virtual directory, IIS receives Web browser requests and passes them to the ISAPI

component of Exchange 2000 Server (DAVEX.DLL).

The following stages are utilized in accessing Exchange 2000 Server:

1. WWW Publishing receives a browser request for an item in a virtual directory.
2. The WEB service of IIS determines the user’s Microsoft Windows 2000 account and performs

an authentication of the user.

3. IIS passes the user’s request to the OWA ISAPI component.
4. If the mailbox is on another computer the local server is configured as a front end system.
5. ExIFS and ExOLEDB communicate with the Information Store service.
6. Based on client permissions, the Information Store permits or denies the user access to the

resources, such as a mailbox.

7. OWA determines how to render the item, requests the data from the Information store.
8. IIS returns the Web page to the user’s Web browser.

Outlook Web Access File Locations

\Program Files\Exchsrvr\Bin. DLL and executable files.

\Program Files\Exchsrvr\Exchweb\Bin. Holds setup files for Outlook.

\Program Files\Exchsrvr\Exchweb\Controls. Location for script files.

\Program Files\Exchsrvr\Exchweb\Lang. Only created if non-English languages are enabled.

\Program Files\Exchsrvr\Exchweb\Img. Logos and other graphic used by OWA.

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Exercise Summary:

You can extend the set of standard virtual directories that provide access to Exchange 2000 Server via

OWA. Using the HTTP virtual server object in Exchange System Manager.

The OWA ISAPI association would be missing. If is not advisable to use the Internet Service Manager

to change the properties of the OWA virtual directories.

Supported Browsers:

Internet Explorer 5.0 is the ideal OWA client. It is a WebDAV-enabled browser that allows

direct manipulation of data on the server.

The following features are available in Internet Explorer 5.0 only:

• Shortcut menus that are displayed when right-clicking on an item
• Drag-and-drop operations between folders
• XML-based data viewing and manipulation
• Native Kerberos authentication (available on Windows 2000 only)
• Preview pane to view message contents in a preview windows without actually opening

the item.

• Tree control to navigate through the hierarchy of mailbox and public folders.

Multimedia Messaging

One of the most exciting features of OWA, if you workstation is equipped with audio and video

features, is Multimedia Messaging. This feature is based on Microsoft Exchange Multimedia

Control, which allows you to record voice and video directly in an e-mail message and send it

as any other messages.

Lesson 2: Outlook Web Access Environments

By default, every user in an Exchange 2000 Server organization can use OWA to access

mailbox and public folders.

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Single-Server Configurations

Single-server environments provide direct access to mailboxes and public servers via the local IIS and the

default HTTP virtual server.

You can create additional virtual servers and assign them a unique combination of IP address, TCP port,

Secure Sockets Layer (SSL) port and host name to create separate Web server instances for users with

different security requirements.

Front End/Back End Configurations

It is a good idea to deploy Exchange 2000 Server in an FE/BE arrangement if you want to support a

large number of users over the Internet.

NOTE: OWA URLs are based on host or domain names. The URLS are independent of Individual

information store information.

Front End Load Balancing

In an FE/BE environment, you can group all your front end systems together for load balancing using

Microsoft Network Load Balancing or another high-performance hardware load-balancing solution,

such as Cisco Local Directory.

Disadvantages of Round-Robin . DNS Round-robin DNS is based on the simple concept

of having the same host name mapped to the IP addresses of multiple front end servers, which

are supposed to share the workload.

Load Balancing and Secure Sockets Layer. Round-robin DNS should not be used for

load balancing across servers if you use SSL to encrypt the communication between the client

and the front end server.

Resource Access

You can control access to OWA resources per HTTP virtual server, virtual directory, and user.

Unfortunately, when working with the default HTTP virtual server, called Exchange Virtual

Server, you have to juggle three different administrative utilities – IIS, Exchange system Manager,

and Active Directory Users and computers.

Controller Access Permissions. IIS is required to manage the properties for the Default Web

Site, which provides access to the OWA virtual directories.

Validated Resource Access. Validated users can work with mailbox and public folders and

can search the Global Address List.

Anonymous Resources Access. All access to mailbox and public folder resources is validated.

By default, the system assigns them the guest account of the IIS, such as IUSR Manchester.

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IMPORTANT: The default HTTP server provides access to public folder properties through the

Exadmin virtual directory. Stopping the virtual server prevents Exchange System Manager from

being able to manage public folder settings. You will receive an error notification that access to

the public folder has failed.

Backward Compatibility Issues

The new OWA is not compatible with OWA of earlier versions of Exchange Server.

During the upgrading of your organization to Exchange 2000 Server, keep in mind that the new

OWA cannot access public folders on earlier versions..

Chapter Summary:

• OWA of Exchange 2000 Server is based on the ISAPI of IIS 5.0
• Based on URLs, IIS determines that Web browser requests must be passed to the ISAPI

component of Exchange 2000 Server, and correspondingly OWA will access mailbox and

public stores through the Microsoft Web Storage System on behalf of the user

• OWA URLs are based on host or domain names. The URLs are independent of individual

mailbox or public store locations.