How to imply SendTextMessageNotificationTo a specific Mailbox

Greetings,

For the last for days, I'm trying to use SendTextMessageNotificationTo in Set-InboxRule to apply it to a Mailbox. Let me explain my progress:

First I created a New-InboxRule by the name of SendSMS

New-InboxRule "SendSMS" -MyNameInToBox $true -FlaggedForAction Any -MarkImportance "High"

then, I Set-InboxRule to:

Set-InboxRule -Identity SendSMS -SubjectContainsWords Urgent -SendTextMessageNotificationTo 5566778899

And without any error, it accepts it. Now I wish to apply this on a Mailbox. I have tried a couple of tricks but everytime, It ask me:

cmdlet Set-InboxRule at command pipeline position 1
Supply values for the following parameters:
Identity: 

If I type the mailbox alias, it say:

The operation couldn't be performed because 'company.local/Users/Administrator\alias' couldn't be found.
    + CategoryInfo          : NotSpecified: (0:Int32) [Set-InboxRule], ManagementObjectNotFoundException
    + FullyQualifiedErrorId : 5312EA90,Microsoft.Exchange.Management.RecipientTasks.SetInboxRule

Now I'm confused on how can I apply it to a specific Mailbox? My target is to send the E-mail which will be received inside the Mailbox and will be CC to the User's Cell phone through SMS.

I am using Exchange 2010 and an SMS Service from NOWSMS. 

Please guide me with your Best knowledge on how can I achieve my target? 

Thank You