I am trying to tell someone (via email) that my friend likes football (English football i.e. soccer) but I'm not sure which one of these it would be.
A él le gusta el fútbol
Le gusta el fútbol
I agree with these answers. Both mean the same thing and are correct, however 'a él...' is more emphatic and I would use this perhaps in a comparison to show clarity such as:
A mí me gusta el baloncesto pero a él le gusta el fútbol
This means "As for me, I like basketball but when it comes to him, he likes football".