Workaround for Yahoo Mail’s hack
July 17th, 2006 by 
emile
It appears that Yahoo Mail doesn't want you pulling in outside stylesheets. When our Trader Interviews email arrived in a Yahoo Mail account, the <link> tag to our CSS was replaced with an <xlink> tag, rendering it unusable. Googling around, it appears that xlink is a valid XHTML tag, but it appears that Yahoo is using it just to break links to outside stylesheets, since they also replace a <body> tag with <xbody>. Our workaround is to replace any <link> tags to outside stylesheets with the contents of that outside stylesheet, before an email is sent. Below is a test file with the function we use to do such a thing.
CODE:
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<?php
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$text = '<LINK href="http://www.traderinterviews.com/main.css"type=text/css rel=stylesheet>Some more text';
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echo StylesheetLink_Replace($text);
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/*------------------------------------------------------------------------------
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Name: StylesheetLink_Replace
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Arguments: html: The HTML to search for <link> tags in
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Returns: The HTML passed in, with <link> tags to external stylesheets
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replaced with the contents of that file
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Purpose: Replaces links to external stylesheets with the actual contents of
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the stylesheet. Yahoo changes the <link tag to <xlink, making the
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CSS not work. Embedding it gets around the problem.
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Notes:
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------------------------------------------------------------------------------*/
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function StylesheetLink_Replace($html)
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{
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/* Find links to CSS files */
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preg_match_all('/<LINK.*href="{0,1}.+\.css"{0,1}.*>/i',
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$html, $whole_links);
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/* Process each css link found */
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foreach($whole_links[0] as $whole_link)
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{
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/* Find the css file path in the match */
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preg_match('/href="{0,1}(.+\.css)"{0,1}/i', $whole_link, $paths);
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/* Open the file and read it into a variable */
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$handle = fopen($paths[1], 'rb');
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/* If the remote file could be opened, do the replacement */
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if($handle)
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{
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$contents = stream_get_contents($handle);
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fclose($handle);
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/* Replace the found string with the contents */
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$html = str_replace($whole_link,
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'<style type="text/css">'.$contents.'</style>',
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$html);
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}
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/* Otherwise, remove the CSS link, since it couldn't be opened anyway */
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else
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{
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$html = str_replace($whole_link, '', $html);
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}
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}
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return $html;
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}
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?>
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