Did you know that you can connect to the Exchange Auto Attendant, and then change/update an existing greeting from home, on a regular phone or from the office, on a OCS endpoint. This can be useful when you have to post an informational greeting telling that the office is closed due to bad weather or something.

Before you can perform this procedure, you need to be assigned permissions. To see what permissions you need, see the "UM dial plans" entry in the Unified Messaging Permissions topic.

This example enables you to manage custom prompt recording using the telephone user interface. You can record custom prompts and greetings by using the TUI if you follow these steps:

1. Create a domain user account that cannot log on interactively.
2. Delegate the Exchange Organization Administrator role to the domain user account.
3. Create an Exchange mailbox for the domain user.
4. Enable the domain user’s mailbox for Unified Messaging.

   Important:

   Allow only those administrators who are managing prompts and greetings access to the extension number and PIN for the domain user account. Use this domain user account only for managing prompts over the telephone.

5. Create a .wav file to be used for the custom greeting for the UM dial plan or auto attendant. Save the .wav file and upload it to a Unified Messaging server.
6. Run the following cmdlet:
1. Set-UMDialPlan -identity MyUMDialPlan -TUIPromptEditingEnabled $true
7. Call the subscriber access number for the dial plan or the telephone number that is configured on the auto attendant. During the playback of the greeting for the dial plan or auto attendant, press the # key and then the * key.
8. Follow the prompts to log on and edit the greetings. You will be prompted for the prompts for the dial plan or auto attendant that you have selected. The prompts in the TUI will let you select the existing prompt or greeting that you want to change.
9. After you have saved the new custom prompt or greeting, the existing .wav file for the prompt or greeting will be replaced.

For more info and original source se How to Enable Custom Prompt Recording Using the Telephone User Interface in Exchange 2007 or Enable Custom Prompt Recording Using the Telephone User Interface in Exchange 2010