looks like opera implemented it according to apple specs and height/width

is required by this browser. without them opera defaults to 100-200 height.
fix for bug.818958

plugins/newmail/setup.php

@@ -235,8 +235,12 @@ function newmail_plugin() {
         }
 
         if ($totalNew > 0 && $newmail_enable == 'on' && $newmail_media != '' ) {
+            /**
+             * docs about embed
+             * Apple: http://www.apple.com/quicktime/authoring/embed.html
+             */
             echo '<embed src="'.htmlspecialchars($newmail_media) .
-                "\" hidden=\"true\" autostart=\"true\">\n";
+                "\" hidden=\"true\" autostart=\"true\" width=\"2\" height=\"2\">\n";
         }
         if ($totalNew > 0 && $newmail_popup == 'on') {
             echo "<script language=\"JavaScript\">\n".

plugins/newmail/testsound.php

@@ -35,7 +35,7 @@ if ( ! sqgetGlobalVar('sound', $sound, SQ_GET) ) {
 echo html_tag( 'table',
          html_tag( 'tr',
              html_tag( 'td',
-                    '<embed src="'.htmlspecialchars($sound).'" hidden="true" autostart="true">'."\n".
+                    '<embed src="'.htmlspecialchars($sound).'" hidden="true" autostart="true" width="2" height="2">'."\n".
                     '<br />'.
                     '<b>' . _("Loading the sound...") . '</b><br />'.
                     '<form>'.