I'd like to add another possibility. At the time of the murder, "instant messaging" was a huge service that many used befored texting became as popular as it is now.
I remember being a member on another forum and a bunch of us became friendly, and we would use instant messaging to chat outside of the forum. One girl used to participate via her phone, while I used the service from my computer.
Basically an account was created using an email address, and then you created a user name . Most of us utilized the user names we were known by on the forum.
This would have been an ideal way for Jodi to create an account, choose TA as a user name, and then send "texts" to whomever she wanted. She wouldn't have needed to hack into anything. Oh, another huge aspect of the service that would benefit the murderess: conversations automatically "disappeared" once the connection ended unless it was manually saved.
IMO the analysis of travis's phone&records showed no evidence that he sent this text.
I just hope the jury got it, cause after reading PS's recap I'm not so sure. I know there has been varied opinion about his posts, but I like to read it b/c it's a perspective from inside the courtroom. I think we tend to understand things a lot more b/c of our ability to bounce ideas and theories off of each other.