EDIT 9/19/2023: This blog post has received significant update.
In this second part of the Demystifying Hybrid Free/Busy, we will cover troubleshooting of Hybrid Free/Busy scenarios, more specifica...
Updated Sep 19, 2023
Version 16.0
Blog Post
Ciao Mirela_Buru,
I have a question for you if you can help me. 
I'm migrating from Google Workspace to Exchange Online. I have implemented availability from Exchange to Gmail by the Availabilityaddressspace and the mailusers that refer to the Google mailboxes. When a migration batch is launched, the system converts the mailuser to UserMailbox, consequently if an Exchange user checks the user's availability, he displays the mailbox status in Microsoft 365 and is no longer able to view the free busy of the account on Google. Since throttling active on Google's part limits the speed of migration, it may take several days for the migration to be finalized and for the user to begin using the mailboxes in Exchange Online.
is there a way to forward the availability request to the source mailbox even the content sync?
Thank you