Re: Is it possible to view mailboxes of all users from a terminal services setup outside of Office 365

Hi Jason,

You can add an Office 365 K plan Exchange Online license to your current subscription and assign this license to your CEO. Then give him the global administrator permission, he will be able to access Exchange Control Panel to see all the mailbox.

After that, he can set up this account in Outlook desktop client using POP and mobile phone using Exchange Active Sync.
Here are the related articles:
Set Up Your E-Mail Account on Your Mobile Phone: http://help.outlook.com/en-US/140/cc511380.aspx
Connect Outlook to This Account: http://help.outlook.com/en-us/140/Dd251217.aspx

However, he will be able to create and remove mailboxes and other operations in your organization if he has global administration.

Thanks,
Vivian Wang