I added some css for links in our newsletter. I put the following text in the editor field, which is shown for the own stylesheet:
a:link {color: #9d77b1;}
a:visited {color: #743d90;}
a:active {color: #743d90;}
a:hover {color: #743d90;}
While editing the mail text the color of the a tags is displayed correctly but when I send the newsletter (as a test mail) it's a totally different color...