Connecting through POP3 or IMAP4 can benefit remote users
Outlook Express's support of POP3 and IMAP4 gives the email client some advantages over other Exchange 2000 Server email clients. For example, because Outlook Express isn't part of Microsoft Office, you don't need to buy a license to operate Outlook Express. In contrast, running Outlook requires that you have a licensed Office installation. (However, if you use Outlook Express with Exchange 2000, you'll need an Exchange server Client Access License—CAL.)
In addition, remote users can use Outlook Express while their machines are disconnected from the Exchange server. This ability is an advantage over the use of Outlook Web Access (OWA), which requires a continuous server connection. POP3 and IMAP4 usually create less network traffic than either Outlook or OWA, and unlike Outlook, Outlook Express can take advantage of Exchange 2000's new front-end and back-end deployment feature to simplify the server namespace and enhance security.
Despite these advantages, using Outlook Express to connect to a corporate Exchange 2000 environment involves some problems and procedures you don't encounter when you use a Messaging API (MAPI) client such as Outlook. Here's how you can properly configure Outlook Express for POP3 and IMAP4 connectivity.
Basic POP3 Configuration
POP3 is the default protocol in Outlook Express, and Microsoft includes an Internet Connection Wizard (ICW) to help users create a POP3 connection. Many users in the enterprise might have previously configured Outlook Express to connect to their ISP-based mailboxes, which can ease both their learning curve and your support costs. But you need to be aware of a few differences in connecting Outlook Express to a corporate Exchange server instead of an ISP's mail server.
To connect Outlook Express to an Exchange server, start Outlook Express and select Accounts from the Tools menu. In the resulting Internet Accounts dialog box, click Add, then click Mail. The first dialog box in the ICW asks for a username. A username has little technical impact; although it controls how the user's name appears in email messages' From field, the username isn't a return address. Ideally, the username matches a user's display name in the Global Address List (GAL).
Click Next, and the wizard asks for the user's Internet email address. This address should match the user's primary corporate SMTP address, not the user's personal (i.e., home) email address.
Click Next again, and the wizard's E-mail Server Names dialog box prompts you for information about the email server. In the My incoming email server is a drop-down list, select POP3 as the server type. Next, fill in the Incoming mail (POP3, IMAP or HTTP) server and Outgoing mail (SMTP) server text boxes with either the Fully Qualified Domain Name (FQDN) or IP address of the POP3 and SMTP servers, respectively. (Be sure you have configured external DNS servers with host records to resolve these FQDNs.) The POP3 server IP address will be either the Exchange 2000 server that hosts the user's mailbox or, if you set up your Exchange 2000 servers in a front-end/back-end configuration, a front-end POP3 server. The SMTP server handles all mail sent from Outlook Express; you need to fill in the SMTP server's address because POP3 is a retrieve-only protocol—it can only read mail, not send it. Depending on your server configuration, the SMTP server's address might be the same FQDN as the POP3 server that you named in the Incoming mail (POP3, IMAP or HTTP) server text box, or the SMTP server might be a different server altogether.
Click Next, and the Internet Mail Logon dialog box appears. You can enter the user's email alias if the alias matches the user's Active Directory (AD) account name and the Exchange 2000 server is a member of the same domain as the user's account. Otherwise, you need to provide names of the domain and AD account in the format DomainName/ActiveDirectoryAccountName/Exchange2000Alias, as Figure 1 shows.
Consider whether you want to select the Remember password check box. Having the system remember the password is user-friendly, but it might create security problems if the user shares the computer with other people. Selecting this box might also lead to problems when the user's password expires and changes at work but not in the user's Outlook Express configuration at home. As a result, the system will reject the user's logon because of incorrect credentials and the user will need to input the new password.
If you select the Log on using Secure Password Authentication (SPA) check box, the Outlook Express client and the Exchange 2000 server will use NT LAN Manager (NTLM) authentication, rather than clear text, to transmit the user ID and password. Consider selecting this check box; the configuration might require slightly more server-end processing and generate more network traffic, but the added security is worth it. For SPA to work, you also need to enable Integrated Windows Authentication on the Exchange POP3 virtual server.
On the subject of security, because POP3 and IMAP4 clients use an SMTP server to relay the mail they send, you risk making your Exchange server into an open relay that spam senders can use to deliver their messages. To block your server from becoming an open relay, see the Microsoft article "Controlling SMTP Relaying with Microsoft Exchange" (http://www.microsoft.com/technet/security/mail/excrelay.asp).
After you finish entering information in the Internet Mail Logon dialog box, click Next. The wizard tells you that you're finished, but you're not. Click Finish, but don't start checking your Inbox for email yet.
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