If you use the online tax form filling facility it just might be OK but I would not trust it. I hope for your sake it's a real email and not spam.
While on this kind of topic. I had a phone call from my credit card company saying they thought my card might have been compromised. I had made a mess of an online order
, therefore it was most likely genuine.
The daft thing is they asked me to give my date of birth over the phone to a strange person in order to proceed. I would never give such information to a cold caller however genuine they are likely to be. I got a letter from them a few days later so it was genuine but how was I to know for sure especially as the caller was foreign.