--- mimemail.theme.inc (6.x-1.0-alpha1)
+++ mimemail.theme.inc
@@ -43,5 +43,5 @@
     if (file_exists($style)) $css .= file_get_contents($style);
   }
 
-  $variables['css'] = str_replace(' ','', str_replace("\n", '', $css));
+  $variables['css'] = preg_replace('#\s+#s', ' ', preg_replace('#\s*([:;,\(\)])\s*#s', '$1',$css));
 }