So I didn't get that email, but I did my re-test seven days ago, and I just got an email saying "Your Official GMAT Online Exam Score is Now Available." The date / test ID listed in the email corresponds to my original test in May, not my re-test in June, and the score on mba dot com is still my original score from May.
I would think/hope that both the email you received and the email I received are technical glitches, and that they would tell us in plain language that our re-test score was lower so our original score is being retained. But honestly who knows with this organization.
Curious to hear from others impacted by this.
EDIT: Never mind, I just got the email with the same subject line as you, but clear language telling me my re-test score was lower and the original score will be retained. So yes, I think that's the email you received too.