i have blocked a person on my iphone but they keep sending me messages by email which reach my messages box on my iPhone, how do I stop this ?

Who is your email provider?

The messages come into my green text messages box (the one with the quotation symbol

Go to Settings/Messages and scroll down to Send and Receive.
Here you can see all the email addresses that can iMessage you and of course your mobile number.
I find the email thing a pain in the bum so I just uncheck ALL the email addresses completely.
Then people can only iMessage to your phone number.
When you have done it it should look like this......
https://www.dropbox.com/s/1lutvq6if1...ssage.JPG?dl=0

In that case you can block the email address in the same way you'd block a phone number

https://support.apple.com/en-gb/HT201229