Sometimes a users mailbox will go corrupt on Windows Exchange Server. This is usually not to hard to fix.... Unless you are on Small Business Server. Then it becomes much harder than it rightfully should be.
You need access to the account effected with Outlook. This is so you can make a backup of the mail box.
You will need administrative access on the exchange server the users mailbox is on.
You will need enough Disk space for the backup for the user. (Depends on mailbox size).
Go to users email account in outlook.
Export everything (to a .pst file).
Make sure to select their top level “MailBox” folder and select the “Export all sub-folders” checkbox.
Once completed log out of exchange with that users account.
Delete the users mail box on the server.
You will need to go to the Server Management Dialog.
Go to “Advanced Management -> First Organization (exchange) -> Administrative Groups -> Servers -> “YourServer” -> Mailbox Store -> Mailboxes.
Right click on the mailbox you will be deleting, Click on “Exchange Tasks”.
On the dialog, select “Delete Mailbox”, Follow the rest of the on-screen instructions.
Now that the users mailbox is marked for deletion, Right click the mailbox list somewhere where there is white space and click on “Refresh”.
You should see a Red X box show next to the mailbox you are deleting.
Right click the mailbox with the Red X and click “Purge” Follow the on-screen directions.
The offending mailbox has now been deleted from the system. Now for the tricky part. Making the new mailbox.
Create a new mailbox for the user.
Make sure you have “Server Management” open.
Navigate to “Advanced Management -> Active Directory Users and Computers -> “YourServer” -> Users”
You will not likely see your user in this list. This is a problem with Exchange on SBS. We do have a trick around this though!
Right Click the white space on the list and select “Find”.
When the dialog pops up the the “In” section change it from “Users” to “Entire Directory”.
Type the users name in the Name field and click “Find Now”.
Once the user is showing in the dialog box, right click on them and select “Exchange Tasks”.
Click on the “Create Mailbox” selection and follow the instructions.
Right click on the user again and again select “Exchange Tasks”. This time select “Configure Exchange Features”.
Run through the dialog to make sure all of the correct features are enabled for the user.
The user should now have a new-clean mailbox. Time to re-import their data.
Log into their Outlook (everything should be empty).
Import everything again.
When you do this make sure to check the boxes like “Replace Duplicates” to make sure everything gets imported as it should.
You should now have a brand new “Fixed” mailbox for your Exchange 2003 SBS user. This may work on different versions of SBS but this is working on a fully patched 2003 SBS server as of April 18, 2011.