Methods for accessing Exchange

The feedback survey I ran a couple of months ago indicated that quite a few nontechnical people read this newsletter and that most readers are interested in reading about Microsoft Exchange-related issues. Consequently, what follows is an overview of the different methods of using Microsoft Outlook and Exchange remotely to help those who are not familiar with the inner workings of the system.

When using Outlook on a LAN, Outlook is connected to an Exchange server in real time, and the user views the contents of the online folders in real time as they are updated. However, remote users have several different methods of accessing the Exchange message store:

* One method is to connect to the server and work as if a LAN connection exists. While performance using this method is acceptable with a broadband connection, a dial-up connection works very poorly. If a VPN connection is also used, performance can drop, although use of Point-to-Point Tunneling Protocol on DSL has been shown to provide LAN-quality performance.

* A second method uses offline folders that mirror those on the Exchange server. These folders are synchronized periodically, which works well over a broadband connection, but poorly over a dial-up connection. If an Exchange administrator configures automatic synchronization, such as for laptop users, synchronization takes place at least twice during a connection. While synchronization carries with it obvious benefits, it can take a substantial length of time to synchronize the server-based mailbox, calendars and contact folders with the local versions.

* A third method is for the user to have a local personal folders file (.PST file) and have Outlook deliver e-mail directly to the in-box, while outbound e-mail is sent directly from the out-box in the local .PST file. While this improves performance compared to automatic synchronization, there are several downsides to this approach. They include the inability to back up users' .PST files adequately because the content is delivered to the local mailbox and removed from the server, and also because remote users are unable to access other online folders like LAN-based users. This method is the least used, since IT support is made more difficult.

* In addition to Exchange-based protocols, Microsoft has also implemented the Internet Message Access Protocol 4, Post Office Protocol 3 and iCalendar protocols. Performance using these protocols can be better than the Exchange-based methods, but the downsides are that holes must be opened in firewalls to permit their use and that additional help-desk training is required.

* Outlook Web access can also be used via a Web browser, but this requires that an HTTPS port be opened in the firewall.

Many thanks to Mark Eisenberg for his contribution to this newsletter, as well as to Brett Clippard.

Michael D. Osterman is the principal of Osterman Research, a market research firm that helps organizations understand the markets for messaging, directory and related products and services. He can be reached by clicking here.

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