domain setting

I have problem in our mail service it is when i send any email from any account in our domain to any person .

my email address appear like that

From: hotmail_------------*** Email address is removed for privacy *** on behalf of it h-----s (it@-------.com)

Sent: Friday, October 25, 2013 2:36:27 PM

To: it --------(it@------.com

and this is for all accounts on this domain

but i find the reason 

in domain setting in domains.live.com

I found under domain setting our service is active and under Edit mail setting 

You can enable mail service for your domain. Please select the mail provider from the choices below. 
No mail 
Outlook.com 

and No mail is selected and i test that when i change to Outlook.com choice the problem is resolver but i found this important notification 

This will permanently delete the existing mailboxes of all users in your domain. All users will be able to continue to use their Microsoft accounts, but will permanently lose their communications data (mail, offline messages).

but i test this on domain have not any important inbox and no thing happen i mean all inbox's is still as it is.

I need assistant if this notification can be happen or not i test that but i need confirmation about that.

I WAIT REPLAY