[cisco-voip] Unity question

[Voll, Scott]

We are going to purchase a second Unity server to integrate with our PBX
until all users upgrade to the new IP Phones.  ( I know one Unity server
could do both CM and PBX but I'm running win2k3 on my current box and
don't want to downgrade to later have to upgrade again.)  Since I'm
using Exchange and AD 2003 do I need to have a VPIM license to get both
Unity servers talking to one another?  

Thanks

Scott