Throw an email to
support@zimbra.com and they should be able to get you the one you require.
*Points at >
4.5.9 (granted you may be on a large install/not have the time etc)
Though not needed, (
http://www.zimbra.com/forums/apple-i...c-leopard.html) you'll get better support on .9 if you eventually get any leopard users. And you'll be in a generally better position when 5.0 does roll out.