There have been instances in the past of people reporting that their Out Of Office rules simply do not work anymore. Of course, one of the common reasons for this is that the rules aren’t actually working to Internet recipients, because the Exchange server is not configured to send the OOF message externally. See this MSKB article on how to configure this.
By the way, why is it called OOF? KC Lemson explains why here!
However, what if the OOF message doesn’t work at all? The OOF message is a hidden entry in a users mailbox. The Out of Office Assistant creates a set of two rules in the Inbox subtree. The first contains a Message Class of IPM.Note.Rules.Oof.Template.MicrosoftMessage, whilst the other rule contains a Message Class of IPM.Note.Rules.OoFTemplate.Microsoft. If one or both of these rules are corrupted or unsynchronized with the OOF-enabled indicator, then its possible that the Out Of Office notification may no longer work.
To resolve this, use the Mdbvue32 utility from the Exchange Server 2000 CD-ROM or the Exchange 2000 Server service pack to delete the two entries for Out of Office. Export both the client and server user rules from Outlook for safe keeping, then use MDB Viewer to manually remove all rules from the mailbox. To do this:
1. Find mdbvu32.exe in the supportutils directory on any of the Exchange Server CDs.
2. Run mdbvu32.exe.
3. Click OK to clear the first window that pops up.
4. Make sure that your profile is selected in the Choose Profile window and click OK.
5. Click on the MDB menu option.
6. Click on the OpenMessageStore option.
7. Make sure that “Mailbox- [user's full name]” is selected and click on Open.
8. Click on the MDB menu option again.
9. Click Open Root Folder.
10. In the Child Folders box – double click on “Top of Information Store”.
11. In the next Child Folders box – double click on “Inbox”.
12. Look in the Associated Messages in Fld box. All of your rules are in this box.
13. Once you find the rule that you want to delete then close the properties for that rule.
14. On the MAPI_FOLDER page make sure that the rule that you want to delete is still highlighted.
15. In the “Operations available (select operation, then push Call Function button)” text box, push the drop down button to reveal the list of functions.
16. Scroll down the list of functions until you see “lpFld -> deleteMessages() (ON SELECTED MSGS)” and then click on it to select it.
17. Next press the Call Function button. This will delete the rule that you selected.
18. Press the Close button to exit the MAPI_FOLDER window.
19. Press Close again to exit the next window.
20. Press Close again to exit the last window.
21. Click on the MDB menu option.
22. Click Store Logoff. Then click OK and OK again.
23. Click Session and then click on Exit.