I am trying to migrate to o365 the remaining local mailboxes on an old Exchange 2010 hybrid server, facing a number of issues
First, when I try doing it in the mgmt console it says, "Add a remote forest to the Exchange management console root node"
I've looked at articles that talk about this, I don't recall ever seeing the 0365 org connected in the local mgmt console on this or other ex2010 server, but migrations have happened in the past.
I then tried to do it from PS, first got error "Target user 'User' already has a primary mailbox.'. - OK so I cleared the AD attributes homeMDB and homeMTA and tried again. Now got this error
"You must specify the RemoteOrganizationName parameter. - Not certain what this should be but made it the same as the 'RemoteHostName' parameter for now.
Now it comes up with this errror
What's my best course of action here, should I proceed with 'Adding the Echange forest to console root' as the GUI migration error suggested? are there any other pitfalls to doing this?
Note, this customer on-prem server is also configued to route mail via our DNS mail domain such as 'webmail.customer.ourorg.com. The certificate bound on the on-prem server root domain belongs to our org, not theirs. I don't know if this is affecting it, but it's a thing still. Eventually we are planning to decom this server, so I don't want to reinvent the mail routing at this stage preferably.
Sorry if any of this sounds off, I am not especially familiar with any of this