Hi Phil,
The Exchange server name is only for create a mapi session.
The service mailbox Alias by default have a name like "EnterpriseVault(ExchangeServerName)" look it in Active directory users and computers. You could use the next command for it doesnt promp you all parameters:
EVPM [-?] [-e <Exchange Server>] [-f <input file>] [-m <mailbox alias>]
where:
-?
Displays help information on the utility.
-e <Exchange Server>
Specifies the name of the Exchange server computer.
-f <input file>
Specifies the name and location of the initialization file.
-m <mailbox alias>
Specifies the name of the Enterprise Vault service mailbox.
If you run Policy Manager without any parameters, it prompts for each one.
Regards