VBA is probably your only option to accomplish this.
A solution using VBA:
Copy this simple VBA procedure into an Outlook VBA project :
Sub ChangeSenderName(itm As MailItem)
itm.SentOnBehalfOfName = "Joe TextsTooMuch"
itm.Save
End Sub
Now create an Outlook rule that checks for incoming emails from 0123456789@mms.att.net. I suggest using the condition called 'with specific words in the sender's address'.
Then for the rule action, select 'run a script'. Set the value to the script called ChangeSenderName.
Once you have saved and enabled this rule, any incoming email that matches the sender address will be passed to the VBA code, which will modify it.
Notes on this solution
This code is actually modifying a field called SentOnBehalfOfName. As a result, it only appears to take effect in the Outlook Message View - not when you open up an individual email. I looked into changing the actual sender field, but it is not able to be modified with VBA.
Alternative solutions
Of course, the most elegant way to do this would be to configure the service that is sending the emails, but I am assuming you have no control over that.
Another option is to configure the mail server which receives the emails, to modify the From header before it delivers to your copy of Outlook.
Best Answer
Your problem is that the copied text arrives with its formatting, which should be stripped. There are products that do that, and some browsers support a "copy plain text" operation or extension, but the simplest solution is to modify that option in Outlook.
From Copy and Paste in Outlook Without Messing Up Your Formatting :
Go to Outlook Options => Mail Format tab => Editor Options => Advanced, then scroll down a little ways to the Cut, copy, and paste options. Drop down each option and select "Match Destination Formatting" or "Keep Text Only".
I don't have Outlook 2010, so cannot judge how easy it is to get to these options.