OS X vs OS X Server

[irgsupport]

I'm considering using Zimbra to replace an aging Sun iPlanet Messenger system. I will be using Mac hardware. Was wondering since Zimbra provides everything it needs, do I have to run OS X Server or could I get away with running standard OS X? Zimbra will be the only thing on the machine. About 150 mailboxes.

Thanks.

[jholder]

We support OS X server and OS X workstation PPC and Intel.
Both Network and Open Source editions.