Thanks everyone for your help.
I followed up by phone with the reservation office in Taipei. Took some time to get through but when I did, they were very helpful and asked me to forward the email to them so they could confirm that it was legitimate. They then sent me an email confirming that the initial email was legit and asked me to call the number. I did so and now everything is verified.
As mentioned, it is just an additional credit card security check.