From the email you've received, tap on the 'Read my message' button:
To keep things secure, we'll send you a 6 digit code you'll use to open your message. Tap on 'Send code' :
You'll be taken to a screen to enter the code, but first we need to get it. You may be able to copy it from a notification you receive, but if you don't see one, tap on the back arrow at the top left of the screen:
This will return you to the message you received. Tap on the back button at the top left again:
You're taken to your inbox. Wait for a new email to arrive with a secure email verification code. You may be able to see the code from this screen, but if not, tap on the message to open it:
Make a note of the 6 digit code, then tap on the back button at the top left to return to your inbox:
From there, return to the original email you received and tap on 'Read my message' again. This will return you to the code screen. Enter the 6 digit code you got in the last step and tap on 'Verify code':
You'll be through to your message:
Any attachments on the email can be opened/downloaded by tapping on them.