Outlook Web Access (OWA) is an indispensable application in many organisations because it allows users to check their e-mail from anywhere in the world using only a Web browser. Unfortunately, OWA doesn't always work the way that it's supposed to. In this article, I'll show you what to do when OWA breaks down. What OWA does
An OWA environment is nothing more than an IIS-based Web application with an interface to the Exchange stores. Clients access the OWA site by making a request to the IIS server over port 80 (HTTP) or port 443 (HTTPS). Once the initial request has been processed, the IIS Server asks the client for authentication credentials. The OWA Server takes these credentials and attempts to authenticate the client. Once they're authenticated, clients can access their Exchange e-mail accounts. Problems with OWA
Problems with OWA can usually be traced to one of the following areas:

• The client's Web browser
• The client's connection to the IIS Server
• An IIS problem
• An Exchange problem

Any one or any combination of these problems can keep OWA from functioning. Naturally, some of the problems that I just described are a little tougher to troubleshoot than others. Therefore, I'll start with the easier solutions and build up to the more complex troubleshooting issues. Client problems
There are many different types of OWA problems, but noting what message the client receives often yields clues as to the nature of the problem. For example, a message stating that a Web site can't be found means something completely different from a message indicating that the page isn't displaying correctly. If the client receives a message stating that the OWA Web site can't be found, there are a number of possible causes to investigate. I recommend troubleshooting such a problem by first trying to access the OWA server from another computer. If other computers can access the OWA site, then the problem is likely with the computer-in-question's Internet connection and not with OWA. On the other hand, if none of the computers that you attempt to access OWA through can attach to the OWA server, then you have a more serious problem. The WAN connection linking the OWA Server to the Internet may be down; IIS could be malfunctioning; or there could be an invalid DNS entry that's pointing the OWA server's FQDN (Fully Qualified Domain Name) to an invalid or incorrect IP address. I'll discuss these problems in a bit more detail later on. Another possibility is that the client is able to access the OWA site, but the site displays incorrectly, or the user isn't allowed to log on. Again, begin the troubleshooting process by trying a different computer. This particular problem is often due to someone using an unsupported Web browser to access OWA. However, if you discover that none of your test computers can authenticate into the OWA Server, it's likely that you have an authentication problem on the server end rather than a Web browser problem. IIS connection errors
IIS connection problems and other IIS-related malfunctions are among the most common causes of OWA errors. It's a lot of work to thoroughly troubleshoot IIS problems, but the necessary steps aren't especially difficult. I recommend beginning the troubleshooting process by going to the OWA Server and verifying its connection to the Internet. If you can surf the Web from the OWA server, you can rule out a connectivity problem. Next, go to a computer outside your network and attempt to ping your OWA server. Try pinging first by IP address and then by FQDN. If both pings fail, it probably means that your firewall is set to block ICMP packets and that the server won't respond to a ping. If this happens to you, I recommend trying the ping test from behind your firewall. A failure of both pings could also mean that there is no connectivity between the machine that you're pinging from and the OWA server. This won't apply in this particular case, though, because you've already established that the communications link is good. If the ping by IP address is good but the ping by FQDN fails, then you likely have a DNS problem. Remember that DNS servers resolve FQDNs to IP addresses. Therefore, if a ping by IP address is successful, you can verify that the communications link is good. If this is the case, then the only thing that should cause a ping by FQDN to fail is if the FQDN isn't being resolved.