I can understand how helpful to make your emails more screen reader friendly. I apologize this is not an available feature! We are however always open to ways we can better our user's experience. What screen reader are you or your contacts using? What part of the email is having issues? For instance is text not being recognized, columns read in a confusing order, links not working? Any specific details you may have is helpful information as we'd be happy to submit this feature request to the appropriate teams.