The below article will assist you in granting any user Full Access or Send As Permissions to another exchange mailbox. This process can only be completed by logging in with the administrator credentials by way of the Control Panel.
1. Navigate to http://my.securembox.com. You will need to sign in with the account administrative credentials (e.g. email@example.com). These credentials are provided when the account is created.
2. Along the left side and under the My User section click the User List link. Your user list will now populate in the center tab.
3. Select the user mailbox that you want to grant permissions to and choose Edit User at the top of the panel.
4. The general mailbox information will begin to populate. Select the Microsoft Exchange tab, then Manage Permissions.
5. The current mailbox permissions will load. Please note this may take a couple minutes. Once loaded, you may click on the Load Address Book button to grant new permissions to other users.
6. Click the Save Changes button once the desired permissions have been set.