To add to this, citi recently starting using this to notify you when you reached your spending bonus after signing up for a new card. I've seen it used to load

To add to this, citi recently starting using this to notify you when you reached your spending bonus after signing up for a new card. I've seen it used to load gifs that are countdown timers that once the final time is reached will always display 00:00:00. I dislike this immensely if only because as others have said it ruins the immutability of email. But it does already exist.