@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document domain("mail.google.com") {

/* Change the height to whatever the need is for your screen */

HTML > BODY > DIV:first-child > DIV > DIV > DIV:last-child > DIV:first-child > DIV:first-child + DIV  {position: fixed !important; padding-top:00px !important;background: none !important; padding-left:9px !important; height:652px !important;z-index:9 !important; overflow: scroll !important; padding-right: 10px !important; overflow-y: hidden !important;}

HTML > BODY > DIV:first-child > DIV > DIV > DIV:last-child > DIV:first-child > DIV:first-child + DIV + DIV {margin-left: 172px !important;}

.zYsCRb {position: fixed;}

/* Change the height to whatever the need is for your screen */

HTML > BODY > DIV:first-child > DIV > DIV > DIV:last-child
{overflow: scroll; height: 652px; overflow-y: hidden !important;}

body {position:fixed;}
}