How to add mailboxes to your Outlook Profile:

There are more than one ways to share other persons mailbox.  The procedure here will help you in sharing the entire mailbox of the other person and its sub-folders.  Please note that the person whose mailbox you wish to share has enabled sharing and give you adequate permissions from their mailboxes.

For Outlook 2007:

1.   On the Tools menu, click Account Settings.
2.   Highlight Microsoft Exchange under the e-mail tab.
3.   Select the change button.
4.   Select the More Settings button.
5.   Select the Advanced tab.
6.   Click the Add button and type in the e-mail address of the mailbox that you would like to add to your exchange profile.

For Outlook 2003:

1. On the Tools menu, click E-Mail Accounts.
2. In the E-Mail Accounts dialog box, click View or change existing e-mail accounts, and then click Next.
3. Click Microsoft Exchange Server in the service box, and then click Change.
4. For the Exchange Server Settings, click More Settings.
5. On the Advanced tab, click the Add button.
6. In the Add Mailbox box, type the name of the mailbox owner.
7. Click OK twice.

Related Links :

Hosted Apps – Exchange SharePoint

Business Email Hosting

Hosted SharePoint Exchange Services

Free SharePoint Hosting Templates

Hosted Exchange Provider