Adding to Keith's response, please read these docs as they will help prevent issues.
Understanding How Exchange 2000 Storage Limits Work with Cisco Unity (Versions 4.0, 3.1, and 3.0 with Microsoft Exchange)
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_white_paper09186a00800faf0f.shtml
Configuring Exchange for Maintenance Tasks
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_maintenance_guide_chapter09186a00801c1ebc.html
Configuring Cisco Unity to Automatically Delete Messages
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_tech_note09186a00800d6824.shtml
If you had installed regular Exchange server and find yourself in a position where Unity won't start as a result of hitting the 16 Gig limit, here is a doc that will get you out of that jamb:
Exchange Server Mailbox Store Does Not Mount When the Mailbox Store Database Reaches the 16-GB Limit
http://support.microsoft.com/default.aspx?scid=kb;en-us;828070&Product=exch2k
excerpt:
To resolve this issue, new functionality has been added to Exchange 2000 Standard Edition that allows an administrator to:
Temporarily increase the database size limit by 1 GB.
Selectively remove unnecessary database content.
Defragment the database to reduce the database to a level that is in the defined boundaries of the database size.
You will need to download:
September 2003 Exchange 2000 Server Post-Service Pack 3 Rollup
http://support.microsoft.com/default.aspx?kbid=824282
After you are able to get Exchange to work properly again, you might hit the same problem again and might want to upgrade Exchange to Enterprise edition.
XADM: Upgrading From Exchange Server Standard Edition to the Enterprise Edition http://support.microsoft.com/default.aspx?kbid=170280
