i'm not sure that's a valid assumption - osx is a minute fraction of desktops, great os though it is, and lots of companies dont use outlook as policy. although of course i understand why zimbra would go for the far more mature outook/isync option first of all, caldav looks exciting as a unifying standard. it would be nice if zimbra supported open standards so that we can use the other 2/3rds of zimbra other than imap with open standard clients. thunderbird has very good imap and ldap support for synchronizing with servers and is a nice corporate client, although has its flaws.I think the Outlook Connector and planned iSync adapter provide the tools neccessary for 80-95% of desktop deployments (assuming most users run Outlook or Mail/iCal). Thunderbird does a poor job of synchronising to anything (just try syncing a PDA with Thunderbird/Sunbird) which makes it very difficult to blame Zimbra for not being able to deploy within the network.