Backing up a partially migrated mailbox

[Jethron]

Regarding mailbox migration to O365: I have all of our Exchange 2010 on-premise mailboxes migrated to the 95% mark. We are ready to start manually completing the batches department by department. Do I have to wait until a mailbox has been 100% migrated to O365 before Veeam Backup for O365 can start backing it up? I'm not really sure if it is in an actual mailbox state when it is only at 95%.

[Mike Resseler]

Hi Jed,

To be honest, I am not sure what it means when a mailbox in O365 is in the 95% state. But I do assume that your users already connect to the O365 mailbox to see and retrieve the data that is migrated already? If so, it means that the API's are reachable, and then it means we can start protecting the data because we use the same connections

Testing would actually be easy. Just create a job with one mailbox at the 95% stage and see if it starts downloading data, which my guess is it will.

Sorry for not having the certain answer
Cheers
Mike