urgent help on admin email

email  received by my user on their registration confirmation,or tell a friend or share video is send by my webhost email account on the behalf of my site ,like this from :username@mysharehostaccount on the behalf of my site name .com(bienvenue@espacechretien.net)

 which look a bit unprofessional,i would prefere just only from:bienvenue@espacechretien.net

i change the emails as advise in the inc,header.inc php at permission 0644,dolphin seem not to read it ,even that i set the permission  now to 777 it is still the same i change my default account email,done email authentification but ,still the same.
 this issue is on hotmail,i know they have block recently some email but i can send mail to hotmail just the from header that i don't like. even from my cpanel webmail i can send mail to hotmail.

i welcome ur solution,thanks