By default, Outlook.com centers your email by placing it inside a div with a class named “ExternalClass” using the styles display:inline-block; line-height: 131%. These have no effect when using IE, however in every other browser, the email will not be centered.
To overwrite these styles and a number of additional fixes simply include the following CSS .ExternalClass within the <head></head> of your emails HTML:
HTML
<style type="text/css">
/* Center your email in Outlook.com */
.ExternalClass {width: 100%;}
/* Overwrite Outlook.com’s Embedded CSS */
table {border-collapse:separate;}
a, a:link, a:visited {text-decoration: none; color: #00788a;}
a:hover {text-decoration: underline;}
h2,h2 a,h2 a:visited,h3,h3 a,h3 a:visited,h4,h5,h6,.t_cht {color:#000 !important;}
.ExternalClass p, .ExternalClass span, .ExternalClass font, .ExternalClass td {line-height: 100%;}
</style>
