New-Mailbox -Name "First last" -Alias "flast" -FirstName "First" -LastName "Last" -DisplayName "First Last" -OrganizationalUnit "example.com/users" -UserPrincipalName "flast@example.com" -Password (ConvertTo-SecureString -String 'password_complying_to_ad_password_policy' -AsPlainText -Force)