Translation:He needs to open his email.
Email is most usual in uk no -, it has become a word in its own right. Also it is abit like sheep singular or plural for some users.
Then you'd likely use the definite article and say 'He needs to open THE email'.
necesita goes with "he, she, it"; necesito is for "I"
(you is necesitas, we necesitamos, you pl and they is necesitan.)
I wrote the correct answer, yet what I wrote was offered back by DuoLingo as an ALTERNATIVE !?