http://cisco.com/en/US/products/sw/voicesw/ps2237/prod_troubleshooting_guide_chapter09186a00801ba57a.html
To Resynchronize MWIs
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Step 1 On the Windows Start menu on the Cisco Unity server, click Programs > Cisco Unity > Manage Integrations. UTIM appears.
Step 2 For the integration node, click the Properties tab.
Step 3 In the MWI Synchronization section, click Resynchronize Now.
Step 4 If applicable, check the Resynchronize At check box, and choose the time that you want the system to resynchronize the MWIs. We recommend choosing a time outside of regular business hours because of the Cisco Unity resources needed for resynchronization.