Office 365 migrations from other providers can be done through your Administrative Portal. (you can access the Portal through your nvArea, under the Hosting Services, Manage Hosting section).
You would start by clicking on the Admin button.
Once in the administrative side, click on the Setup option.
On the bottom of the page, under the Data Migration option. You can choose to Migrate your user’ data option to move mail from another service.
You would select the appropriate service you wish to migrate from and enter the hostname, port, and login details.
Once saved you will go to the active migrations page with 2 boxes to fill out, enter the first part of the email address (prior to the @ symbol), then in the second box, the email account’s password, and hit the Start Migration button.