When migrating users the following error was seen in the log file and no mail was migrated to Office 365
ERROR: [7444-1-157-00000000] ADFWD::AddProxies (1): Processing 'CN=FN SN,OU=Internal,OU=Users,OU=Accounts,DC=Org,DC=com'
Expected to find mail-enabled object to add address(es) to.
In the Migrate User Account wizard "Verify Target Address" had been set and this option cannot be used in an Office 365 migration scenario.
Uncheck the "Verify Target Address" checkbox and proceed with the migration. This is only for an Office 365 migration scenario