I have question about a hosted zimbra server using multiple domains:

companyA.com and companyB.com are on the same zimbra system

both companyA and companyB are constantly growing and adding users & departments. The Zimbra web client is used extensively. Neither company knows they are hosted on the same Zimbra Platform.

end users from each company use the Calendar / Schedule to add people to new events. If users from either company invite users of the other company, Zimbra provides free/busy state!

Ah hah! you say, have the end-user preferences / calendar / permissions / Free/Busy area should do the trick. ...Well how does one allow "ALL" users from just their company/domain ? If users are constantly adding and removing in a company, asking each user to manage the "allow" list, or having an admin handle this sounds tedious.

Any advice?

This was tested on 5.09 NE