After creating an Archive Database in Exchange 2010, you find that Exchange will put new user mailboxes on this database, in order to balance mailboxes across stores. The easiest way to avoid this is to exclude the Archive Database from your mailbox provisioning.
Using Exchange 2010 Powershell, get a list of your mailbox databases by running Get-MailboxDatabase:
Once you confirm the name of your archive database, exclude it from automatic provisioning by running the following PowerShell command: Set-MailboxDatabase -Identity “Archive Database” -IsExcludedFromProvisioning $True
I have recently been utilizing MigrationWiz https://www.migrationwiz.com/ for some of my Office 365 migrations. The easiest way to do this is my utilizing an admin account – both on your Exchange on-premise or 3rd party hosted solution & on Office 365. In order to this, simply connect via Powershell and ran the following commands:
$LiveCred = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred -Authentication Basic -AllowRedirection