Hi Zeeshan,
The assumption here is that the email account (for the clients) already exists :) There is no second mail box to configure. Here are some related notes;
Internet Message Access Protocol (IMAP)-based email client to access voice messages
- Access email and voicemail messages and play and delete voice messages from the same desktop email client.
- Voice messages in your email inbox are synchronized with the MWI on your telephone.
- Various standards-based desktop email clients are supported, including Microsoft Outlook, Lotus Notes, and Entourage for Mac.
Configuring an E-Mail Account to Access Cisco Unity Connection Voice Messages
http://www.cisco.com/en/US/docs/voice_ip_comm/connection/2x/user_setup/guide/2xcucus030.html#wp1049832
Hope this helps!
Rob