exchange hybrid: migrating mailboxes
migrating to office365:
user account must be synced (dirsync/aadsync)
on-prem mailbox needs to have domains not added to office365 tenant removed
exchange online license applied
outlook client users with a cloud mailbox will need to enter their credentials at least once after the migration takes place.
as of oct 2015, onboarding is maxed at 1GB/hour for data transfers. it’s recommended to migrate mailboxes with delegate access rights together.
migrating from office365:
on-prem remote mailbox object must have correct GUID, see here for resolving mismatches: https://support.microsoft.com/en-us/kb/2956029
choose on-prem database and domain
remote mailbox will be converted to user mailbox
if migrating all mailboxes to office365 then a hybrid is useful for using on-prem EAC for management (reduced cost exchange hybrid license can be used). also on-prem exchange can be used for relaying unauthenticated smtp traffic.