Actually i need to do this
When a customer gets rewards points he gets notified by email. The default email contains only these lines :
You have received 200 Reward Points!
Your total number of reward points is now 200.
$_['text_reward_received'] = 'You have received %s Reward Points!';
$_['text_reward_total'] = 'Your total number of reward points is now %s.';
I was unable to add html in language file because in model the method used to send mail was using
$mail ->setText(html_entity_decode($message, ENT_QUOTES, 'UTF-8'));
I have changed this to :
$mail ->setHtml(html_entity_decode($message, ENT_QUOTES, 'UTF-8'));
It then allowed me to add html in language file.