In a tip on March 16 (Is IIS to blame for OWA problems?), I discussed how errors with Outlook Web Access (OWA) could be caused either by the IIS server or by the Exchange server. The reason is because the two are tightly coupled, and what looks like an error that Exchange is throwing out could easily be caused by the other server, and vice versa.
But if you're having users with problems caused by IIS, then the next question is what do the errors mean? For instance, suppose your user is getting a 404 Not Found error. What does that mean? This could happen when a user looks at a mail message that appears on the OWA Web page, but when he clicks on it, he finds that he gets a 404 Not Found message.
Well, a 404 is a 404. For some reason, the request to look at that message couldn't be completed because the server could not find the item. One possible explanation is so simple that you might not even think of it. Suppose your user had called up his Web page (perhaps on a system away from his normal workstation) and then, for some reason, left that system and returned to one on which he has his Outlook client open. There he reads the message and deletes it. Later, returning to the OWA page, he clicks on the message again. Result? 404.
In this case, there really is no error, because the object your user is trying to view really isn't available. But the OWA view doesn't automatically refresh, so a user who isn't paying a lot of attention could get into just this kind of situation, and wonder what happened.
In another situation, your user is getting a 401 error, either Access Denied or Logon Failed. There are any number of possible causes. The simplest, of course, is that the user didn't enter his username or password correctly. It's a good idea to make sure that users don't have their CapsLock key on. When you set up a computer for a user, turn off the CapsLock key on boot-up, just so users don't forget to turn it off before entering a password. Also, make sure you tell your users that they should always retype their username and password in the case of a logon failure, just on the off chance that the user made some sort of a typo.
Or, if the user is trying to access OWA on a newly created account, then it could be that the account hasn't been properly initialized by the server. You can wait a few minutes, or you can try sending a message to the account, which may be able to speed up the process.
These troubleshooting tips are available in a document on the Microsoft Web site. You can download the file that you find there, and keep it for ready reference when the inevitable errors appear as your users access OWA.
David Gabel has been testing and writing about computers for more than 25 years.