Remove webmail link from toolbar

If logged in via server iP address, the variable points to the wrong address. 

Connecting to 0.0.0.0/webmail/ is also not supported.

Webmail access link will be moved into the quick action toolbar, which can generate the correct URL based on domain name.

web/templates/admin/list_mail.html

@@ -17,7 +17,6 @@
                   $webmail = "http://webmail.".$http_host."/";
                   if (!empty($_SESSION['MAIL_URL'])) $webmail = $_SESSION['MAIL_URL'];
                 ?>
-                <a class="vst" href="<?=$webmail?>" target="_blank"><?=__('open webmail')?> <i></i></a>
               </td>
               <td class="l-sort-toolbar__search-box step-left">
                 <form action="/search/" method="get">

web/templates/admin/list_mail_acc.html

@@ -16,7 +16,6 @@
                   $webmail = "http://webmail.".$http_host."/";
                   if (!empty($_SESSION['MAIL_URL'])) $webmail = $_SESSION['MAIL_URL'];
                 ?>
-                <a class="vst" href="<?=$webmail?>" target="_blank"><?=__('open webmail')?> <i></i></a>
               </td>
               <td class="l-sort-toolbar__search-box step-left">
                 <form action="/search/" method="get">

web/templates/user/list_mail.html

@@ -17,7 +17,6 @@
                   $webmail = "http://".$http_host."/webmail/";
                   if (!empty($_SESSION['MAIL_URL'])) $webmail = $_SESSION['MAIL_URL'];
                 ?>
-                <a class="vst" href="<?=$webmail?>" target="_blank"><?=__('open webmail')?> <i></i></a>
               </td>
               <td class="l-sort-toolbar__search-box step-left">
                 <form action="/search/" method="get">

web/templates/user/list_mail_acc.html

@@ -16,7 +16,6 @@
                   $webmail = "http://".$http_host."/webmail/";
                   if (!empty($_SESSION['MAIL_URL'])) $webmail = $_SESSION['MAIL_URL'];
                 ?>
-                <a class="vst" href="<?=$webmail?>" target="_blank"><?=__('open webmail')?> <i></i></a>
               </td>
               <td class="l-sort-toolbar__search-box step-left">
                 <form action="/search/" method="get">