When inserting a link in a message,you might want to change the automatic styles that is applied. For exemple, you might want to remove the blue underline that appears on your links. 

To do so, open the messge editor and edit text block where the link appears and add following code : style="text-decoration:none"

Here is aa article to learn more : https://www.w3schools.com/cssref/pr_text_text-decoration.asp