I am trying to convince people from my organization to migrate to Zimbra.
The big pushback is not so much the migration or getting used to a new tool.

The big pushback is how a user will be able to "interact" with her management if the management does not move to Zimbra.
One critical feature seems to be calendering and especially meeting scheduling.

Is there a way to have access to free/busy information from a non Zimbra user?
Is there a way to have access from Exchange to Zimbra users's free busy info?