While the Exchange Server 2000 exam focuses mostly on server related issues, you will find some questions that deal specifical

While the Exchange Server 2000 exam focuses mostly on serv= er related issues, you will find some questions that deal specifically with cl= ient connectivity. To that end, we will address the topics that you might find on the exam. First, you will need to know about the types of clients that can connect to Exchange Server, and then specifically how to configure Outlook = Web Access (OWA). We will address OWA in a following article, and then in a fut= ure TechCenter article we will also show you how to configure SMTP virtual serv= ers and some common client connectivity scenarios, including how we would go ab= out troubleshooting problems.

Exchange 2000 Clients

With Microsoft Exchange Server 2000, there are a number of different ways for clients to connect to a server. Depending on the protocol used to connect, different levels of functionality are available. We will examine these common metho= ds of accessing Exchange Server from a client computer:

* = Microsoft Exchange Server Service

* = POP3

* = IMAP4

* = HTTP

Configuring properties for these protocols occurs both on = the server and on the clients. Server settings are configured using the Exchange System Manager, by navigating down the tree to Organization->Admi= nistrative Groups->First Administrative Group->Servers->servername->= ;Protocols->protocol name.

Microsoft Exchange Server Service

The Simple Mail Transport Protocol (SMTP) is the native communication mechanism within Exchange 2000. It has been the standard prot= ocol for transmitting email over the Internet for many years, and as Microsoft h= as embraced open standards it has become the standard for Exchange 2000 as wel= l, replacing the proprietary MTA mechanisms.

Outlook 2000, when running in "corporate or workgroup= " mode, can connect and login to a mailbox on an Exchange server. In this mod= e, the entire feature set of Outlook 2000 is available to the user, which incl= udes all of the email, calendaring, tasks, notes, and journaling available in a standalone mode, plus the ability to share any of this information with oth= er users in the Exchange organization and the ability to use Public Folders. T= his mode utilizes the Microsoft Exchange Server service, which can be seen in Outlook by clicking on Tools->Services. The information presented in this section will assume Outlook 2000 has been configured in this full-featured corporate or workgroup mode.

Configuring Outlook 2000

Once Outlook is installed, use the Mail applet in Control = Panel to setup a profile to connect to an Exchange server. Click "Show Profiles," and then "Add," and then follow the steps in the wizard. To connect to an Exchange server, you will only need to select the Microsoft Exchange Server service from the list of available services. You = will need to know the name or IP address of your Exchange server, and the mailbox name or alias. Multiple profiles can be setup on a single computer to allow different users to use the same Outlook 2000 installation to login to an Exchange server with their own distinct configuration. At the bottom of the Mail applet is a drop down list to select the current active profile. Alternatively, you can go under Tools->Options in the Outlook client and click the Mail Services tab to set the default profile or even have Outlook prompt for a profile to be used if Outlook is normally used by multiple peo= ple. An example of when you would do this is what we do at the company I work fo= r, where we have outside sales people who primarily work from home, but stop i= n at the office at various points of the day, such as between meetings. We have several shared computers setup where the sales reps can login and check the= ir email and calendars and could even synchronize their PDAs with their Outlook profiles if they needed to.

The SMTP Mail Process with Outlook 2000

When a user sends an email using Outlook 2000, the message= is sent to the Exchange server over port 25, the Internet standard for SMTP messaging. When the message arrives at the server, it is placed in the Queue directory. From there, Exchange determines whether the destination address = is local or remote. If it is local, Exchange places the message directly into = the appropriate information store. If it the destination is remote, Exchange wi= ll sort the messages in the queue in an attempt to optimize delivery. It does = this by separating messages out by domain, so that it can attempt to deliver all messages destined for a single domain at one time.

Once the messages are sorted, Exchange will use a configur= ed SMTP virtual server to contact the remote SMTP server to see if it is ready= to accept delivery of the messages. If the server is not ready, the message wi= ll stay in the queue for a configurable length of time before delivery is attempted again. If the server is ready, communication between the two serv= ers takes place to determine if the recipients are valid, and if they are, mess= age transfer takes place.

The properties for Outlook are configured both on the Exch= ange server and the Outlook client. Properties such as message limits, delivery restrictions, and security are configured through the Exchange System Manag= er and Active Directory Users and Computers, while properties such as granting access permission to other users and message delivery format are primarily configured through Outlook.

POP3 Clients

Outlook 2000 establishing a connection directly to Exchang= e 2000 works great when you have constant communication between client and server, such as when connected over a LAN or even a VPN. However, there are many ti= mes when communication between client and server cannot be reliably maintained.= For that reason, Exchange 2000 also supports the Post Office Protocol 3 (POP3) Internet message protocol. A POP3 client connecting to an Exchange server d= oes not enjoy all of the benefits of the Outlook 2000 SMTP communication discus= sed in the previous section. POP3 only gives access to a user's inbox, and will simply connect, download email messages from the user's inbox, and disconne= ct. POP3 communication occurs over TCP port 110. If you are using Secure Sockets Layer (SSL) security, POP3 will also utilize port 995.

To use POP3, a user must have a mailbox enabled account on= the Exchange server. Outlook 2000 can be used as a POP3 client, either by configuring it in Internet Mail Only mode, or by adding instances of Intern= et Mail to run alongside the Microsoft Exchange Service under Tools->Servic= es in Outlook. Outlook Express, however, is the more commonly used POP3 client= as that is what it was designed for.

Configuring POP3 again follows a wizard format. As with configuring the Microsoft Exchange Service, you have to know the name of yo= ur mail server, and your username and password. You can configure advanced opt= ions as well such as having the email left on the server and how often the POP3 client should contact the server to check for new messages.

By default POP3 deletes the email from the server upon download, which causes many people problems when they download email at home and then go to work the next day and find their inbox empty.

IMAP4 Clients

The Internet Messaging Access protocol 4 (IMAP4) protocol provides a compromise between the constant connection requirements of the Microsoft Exchange Server Service and the offline nature of POP3. IMAP4 also requires a mailbox-enabled user account in order to logon, but rather than downloading the messages from the server, IMAP4 allows the user to manipula= te their mailbox directly on the server. This is especially beneficial if a us= er logs in from multiple workstations, because email always stays on the server it is available from everywhere, just as with th= e Microsoft Exchange Server service.

Another advantage of IMAP4 over POP3 is the ability to acc= ess more than just the inbox. IMAP4 users can access public folders if configur= ed by the administrator. IMAP4 is used for receiving messages, but doesn't han= dle sending messages. The SMTP protocol is used instead. IMAP4 communicates over TCP port 143. If you are using SSL security, IMAP4 will also utilize port 9= 93.

While IMAP4 works better than POP3 for handling email, it = does not support the full feature set of Outlook and cannot be used to access calendaring functions or task lists for example. That is what makes it a compromise between the Microsoft Exchange Server service and POP3.

When accessing messages, the IMAP4 protocol's retrieval performance can potentially be increased by selecting the option for "Enable fast message retrieval," which tells Exchange to approxim= ate the message sizes it reports back rather than calculating an exact size. Th= is, however, can cause problems with some IMAP4 clients that require exact mess= age sizes. Additionally, some IMAP4 clients can have trouble with large public folder lists. By default, Exchange will report all public folders when a li= st is requested by a client. If you have problems with IMAP4 client connectivi= ty, you might look at these two settings, which are illustrated in the figure below.

HTTP Clients

Using the Hyper Text Transfer Protocol (HTTP), Microsoft h= as made the features of Exchange Server available to anyone who has a web brow= ser. This type of connection is commonly referred to as Outlook Web Access (OWA). There is no offline mode, so everything you view is on the server, making it convenient for accessing your server when offsite. There are some limitatio= ns though, OWA doesn't support the entire feature set of the Microsoft Exchange Server service running through Outlook 2000, especially when it comes to calendar management. Therefore, it should not be considered a replacement f= or Outlook 2000, but rather something to compliment it. For non-Windows client= s like those running Linux or Unix, OWA is the only mea= ns of connecting to an Exchange server and accessing features beyond mail, such as the calendar, task list, notes, and journal.

Technically, OWA uses extensions to the HTTP 1.1 protocol defined in RFC 2518 called WebDAV. This is also referred to as HTTP-DAV, wh= ere the DAV stands for Distributed Authoring and Versioning. WebDAV prov= ides advanced features such as file locking (prevents multiple users from writin= g to a file simultaneously) that makes the web a collaborative medium, and enabl= es users through OWA to read and write information to their mailbox without ha= ving to download it to their hard drive first. OWA communicates over TCP port 80, which is the standard for HTTP traffic. If Secure Sockets Layer (SSL) is us= ed, port 443 would be used as well.

Next time, we will examine configuring OWA for IIS authentication and access through a firewall.

Questions or Comments? Will can be reached at WWillis@Transcender.com