bulk user creation with archive creation

i wanted to create 1000 users for my organization. i have created a csv file with the following field :

Firstname,lastname,Name,Alias,userprincipalname,database,organizationalunit,archivedatabase,password

then i import it using the following powershell :

Import-CSV bulkuser.csv | foreach {new-mailbox -Name $_.name -Alias $_.alias -UserPrincipalName $_.userprincipalname -Database $_.Database -archivedatabase $_.archivedatabase -OrganizationalUnit $_.organizationalunit -password(ConvertTo-SecureString $_.password -AsPlainText -force)}

the users were created successfully, the name, the database and etc...

BUT, the archive database don't seem to work.  the archive database wasn't enable for the users.  the archive db was already created before I run the script.

Any thought?