Legal Question in Business Law in Texas

I'm not sure what you mean by certify. For an email to be admissible and highly credible, you will need the company which controls the email server to produce the email, along with all the information regarding the email (metadata, any database entries on the email), and then have a custodian of records prepare an affidavit that the records are true and correct and of the type they normally hold for business purposes. In order to be more convincing, you may wish to have an expert testify on how email is sent, stored, retrieved and the email providers security. Testimony of the sender or recipient, if available, may also be necessary.

As a practical matter, in small law suits that I have had in lower courts where such authentication would be impractical and too expensive for my clients, I have simply proffered the email and had the sender or recipient testify to its authenticity. The judges always admit them, and I've won all the cases, so we can only assume that the emails had some probative value to the judge (since we don't receive detailed rulings at this level). If its a million dollar case, don't expect to win by just waltzing in with printouts, though.