on zimbra to route mail to exchange the zmprov md command need to be executed
Split Domain - Zimbra :: Wiki


Exchange 2010 Free/Busy Interop - Zimbra :: Wiki

after more investigation it appears that the fqdn parameter is the actual SMTP namespace that the free busy will be accessed from.

Cross-Forest Availability with Exchange 2007 and Exchange 2010 :...

Is this sufficient permissions or overkill?
'Zimbra' account will be used for F/B and GAL Interaction.
'Zmigrator' account will be used for migration functions(mapi profile, mailbox access).
...

when this command is executed:

Add-AvailabilityAddressSpace -forestname ZimbraFQDN -accessmethod Publicfolder

does this just provide access and updates from Zimbra free busy info to the...

Add-AvailabilityAddressSpace -forestname <ZIMBRA SYSTEMS's FQDN>
>
> -accessmethod publicfolder
>
>
>
> This command references Zimbra’s System FQDN. What would this be
> exactly – the...