Login to the webmail and click the Settings button
Click [Folders] in the Settings List
To subscribe share folders - You will see them on the Folders list, all under "shared" - To subscribe firstname.lastname@example.org's Inbox, just check the checkbox which besides the "INBOX"
To share folders - Click the folder you want to share (for example, the Inbox) - On the Sharing section, click [+]
- In the popup, input the email address you want to share to - Select the Access Rights and click [Save]