Raj, you'll want to use a MAPI editor to look at the properties of one of those voicemails and see the message class. It might be something like IPM.Note.Voice.Unity, for example, if your company uses Cisco Unity. This is from the EV help file:
Directory Properties: Exchange Message Classes
The list shows those message classes that are known to Enterprise Vault.
Message Class. This column shows the names of the message classes that are known to Enterprise Vault.
Description. This column shows a text description of the message class.
Add. Click Add if you want to add a new message class to the list.
Remove. To delete a message class from the list, click the class to select it and then click Remove. Enterprise Vault no longer automatically archives items in this class.
This list does not define the message classes that Enterprise Vault archives. The list shows the message classes that are available for selection in Enterprise Vault Exchange policies. To control which message classes are archived during an archiving run, you need to select the required message classes in the Message Classes property page of individual archiving policies.
Users can manually archive items from any message class, not just those that are listed here.
If you want to prevent Enterprise Vault from archiving a specific message class during an archiving run, add it to this list and make sure that it is not selected in the Exchange archiving policies.
If the message class is selected in an archiving policy, Enterprise Vault archives items whose message classes match the text listed. You can use a trailing asterisk as a wildcard. For example, a message class of IPM* would include IPM.Appointment, IPM.Contact, IPM.Document, and so on.
