OOF on additional mailbox

I’ve been assigned an additional Exchange mailbox and I’ve configured it to show in my Outlook folder list. When I enable the Out of Office Assistant in Outlook, it only works for my own mailbox.
How can I enable the Out of Office function for this additional mailbox as well?

Most of Outlook’s Exchange specific functionalities such as the Out of Office Assistant (OOF) only work for the main mailbox.

If you have been assigned Full Mailbox permissions by your Exchange administrator (verify this with him/her if you do not know; delegate permissions is not enough!), then there are 2 ways in which you can enable the OOF on an additional mailbox.

Additional mail profile
As the Exchange features only work for the main mailbox, you can create a separate mail profile with the secondary mailbox as the main mailbox. To change the OOF status, you’d then restart Outlook with the separate mail profile. After you have changed the status, you can restart Outlook again with your normal mail profile.

You can find more information about how to create an additional mail profile here. If you are using Outlook 2007, make sure you select to configure your mail account manually or otherwise it will be created with your own mailbox as the main mailbox instead of the additional mailbox.

Outlook Web Access
If you have access to Outlook Web Access (OWA), then you can also change the OOF status there. Ask your Exchange administrator if you don’t know how to reach OWA in your organization.

Once logged in to OWA, the way you access the additional mailbox depends on the version of Exchange and how much customizations have been put into the design by your company.

When using Exchange 2007, you can click on your name at the right top corner (next to Log Off) to access the “Open Other Mailbox” dialog.

When using Exchange 2003 or Exchange 2000, you can modify the URL to access another mailbox. For instance;
Assume your OWA URL is: http://mail.yourcompany.com/exchange

In order to access the mailbox called “test” you simply type;
http://mail.yourcompany.com/exchange/test

If you want to use this trick in Exchange 2007, you’ll have to use an email address associated with that mailbox;
http://mail.yourcompany.com/owa/test@yourcompany.com