I want to style mail body. I have tried the below methods to style mail body. But all of them didn't work

1) Used external style sheet style.css

td{padding:10px;}   

mail.php

<link rel="stylesheet" href="style.css"></link><table><td>....</td></table>

2) Defined Internal Style Sheet:

mail.php

 <style type="text/css">
td{
    padding-bottom:8px;
}

</style>
<table><td>....</td></table>

I know, Inline style works by doing <td style='padding-bottom:8px'>, But i have got many tables, doing the inline style is not a good idea, Is there any work around so that no need to define style for each element