Index: admin/system_presets/simple/users_u.php
===================================================================
--- admin/system_presets/simple/users_u.php	(revision 14643)
+++ admin/system_presets/simple/users_u.php	(working copy)
@@ -25,7 +25,7 @@
 	// toolbar buttons
 	$remove_buttons = Array (
 //		list of users; section: Users Management -> Users
-		'users_list' => Array (/*'new_item', 'edit', 'delete', 'approve', 'decline', 'e-mail',*/ 'export', /*'view', 'dbl-click'*/),
+		'users_list' => Array (/*'new_item', 'edit', 'delete', 'approve', 'decline', 'e-mail',*/ 'export', 'frontend_mail', /*'view', 'dbl-click'*/),
 
 //		"General" tab during user adding/editing
 //		'users_edit' => Array ('select', 'cancel', 'reset_edit', 'prev', 'next'),
Index: core/admin_templates/users/users_list.tpl
===================================================================
--- core/admin_templates/users/users_list.tpl	(revision 14643)
+++ core/admin_templates/users/users_list.tpl	(working copy)
@@ -7,6 +7,28 @@
 	<tr>
 	  	<td>
 	  		<script type="text/javascript">
+
+				function getFirstSelected()
+				{
+					var items = document.getElementById('kernel_form').elements;
+					var ilength = items.length;
+					var counter = 0;
+					var user_id;
+					for(var i=0; i < ilength; i++) {
+						if(items[i].name.match(/^u\.regular\[.+\]\[PortalUserId\]$/) && items[i].checked == true) {
+							var name_elems = items[i].name.split('[');
+							name_elems = name_elems[1].split(']');
+							counter++;
+							if (counter > 1) {
+								return false;
+							}
+							user_id = name_elems[0];
+						}
+					}
+
+					return user_id;
+				}
+
 	  			//do not rename - this function is used in default grid for double click!
 	  			function edit()
 	  			{
@@ -55,6 +77,22 @@
 
 				a_toolbar.AddButton( new ToolBarSeparator('sep2') );
 
+				a_toolbar.AddButton( new ToolBarButton('frontend_mail', '<inp2:m_phrase label="la_ToolTip_LoginAs" escape="1"/>',
+					function() {
+						var user_id = getFirstSelected();
+
+						if(user_id) {
+							var $url = '<inp2:m_Link t="index" index_file="../index.php" user="#USER_ID#" no_amp="1" />&events[u]=OnLoginAs';
+							$url = $url.replace('#USER_ID#', user_id);
+							window.open($url, 'frontend' + user_id, '');
+						} else {
+							alert('<inp2:m_phrase label="la_error_YouMustSelectOnlyOneUser" escape="1"/>');
+						}
+					}
+				) );
+
+				a_toolbar.AddButton( new ToolBarSeparator('sep3') );
+
 				<inp2:m_if check="m_ModuleEnabled" module="In-Portal">
 					a_toolbar.AddButton(
 						new ToolBarButton(
@@ -75,7 +113,7 @@
 						}
 				) );
 
-				a_toolbar.AddButton( new ToolBarSeparator('sep3') );
+				a_toolbar.AddButton( new ToolBarSeparator('sep4') );
 
 				a_toolbar.AddButton( new ToolBarButton('view', '<inp2:m_phrase label="la_ToolTip_View" escape="1"/>', function() {
 							show_viewmenu(a_toolbar,'view');
@@ -93,6 +131,6 @@
 
 <inp2:m_RenderElement name="grid" PrefixSpecial="u.regular" IdField="PortalUserId" grid="RegularUsers"/>
 <script type="text/javascript">
-	Grids['u.regular'].SetDependantToolbarButtons( new Array('edit', 'delete', 'setprimary', 'e-mail', 'approve', 'decline') );
+	Grids['u.regular'].SetDependantToolbarButtons( new Array('edit', 'delete', 'setprimary', 'e-mail', 'approve', 'decline', 'frontend_mail') );
 </script>
 <inp2:m_include t="incs/footer"/>
\ No newline at end of file
Index: core/install/english.lang
===================================================================
--- core/install/english.lang	(revision 14643)
+++ core/install/english.lang	(working copy)
@@ -1513,6 +1513,7 @@
 			<PHRASE Label="lu_opt_AutoDetect" Module="Core" Type="1">QXV0by1EZXRlY3Q=</PHRASE>
 			<PHRASE Label="lu_opt_Cookies" Module="Core" Type="1">Q29va2llcw==</PHRASE>
 			<PHRASE Label="lu_opt_QueryString" Module="Core" Type="1">UXVlcnkgU3RyaW5nIChTSUQp</PHRASE>
+			<PHRASE Label="la_error_YouMustSelectOnlyOneUser" Module="Custom" Type="1">WW91IG11c3Qgc2VsZWN0IG9ubHkgb25lIHVzZXI=</PHRASE>
 		</PHRASES>
 		<EVENTS>
 			<EVENT MessageType="html" Event="CATEGORY.ADD" Type="0">U3ViamVjdDogTmV3IENhdGVnb3J5ICI8aW5wMjpjX0ZpZWxkIG5hbWU9Ik5hbWUiLz4iIC0gQWRkZWQKCllvdXIgc3VnZ2VzdGVkIGNhdGVnb3J5ICI8aW5wMjpjX0ZpZWxkIG5hbWU9Ik5hbWUiLz4iIGhhcyBiZWVuIGFkZGVkLg==</EVENT>
Index: core/units/users/users_config.php
===================================================================
--- core/units/users/users_config.php	(revision 14643)
+++ core/units/users/users_config.php	(working copy)
@@ -123,7 +123,7 @@
 
 						'users_list' => Array (
 							'prefixes' => Array ('u_List'), 'format' => "!la_title_Users!",
-							'toolbar_buttons' => Array ('new_item', 'edit', 'delete', 'setprimary', 'approve', 'decline', 'e-mail', 'export', 'view', 'dbl-click'),
+							'toolbar_buttons' => Array ('new_item', 'edit', 'delete', 'setprimary', 'approve', 'decline', 'e-mail', 'export', 'view', 'dbl-click', 'frontend_mail'),
 						),
 
 						'users_edit' => Array (
Index: core/units/users/users_event_handler.php
===================================================================
--- core/units/users/users_event_handler.php	(revision 14643)
+++ core/units/users/users_event_handler.php	(working copy)
@@ -115,6 +115,29 @@
 			}
 		}
 
+		private function _hasAdminSession()
+		{
+			$adm_sid = $_COOKIE['adm_sid'];
+
+			$sql = 'SELECT PortalUserId
+					FROM '.TABLE_PREFIX.'UserSession
+					WHERE SessionKey = '.$this->Conn->qstr($_COOKIE['adm_sid']);
+			$admin_id = $this->Conn->GetOne($sql);
+
+			if (!$admin_id) {
+				return false;
+			}
+
+			if ($admin_id == -1) {
+				return true;
+			}
+
+			$sql = 'SELECT GroupId
+					FROM ' . TABLE_PREFIX . 'UserGroup
+					WHERE (PortalUserId = ' . $admin_id . ') AND ( (MembershipExpires IS NULL) OR (MembershipExpires >= ' . adodb_mktime() . ') ) AND GroupId = 11';
+			return ($this->Conn->GetOne($sql) == 11);
+		}
+
 		/**
 		 * Checks user permission to execute given $event
 		 *
@@ -133,6 +156,10 @@
 				return defined('DBG_RESET_ROOT') && DBG_RESET_ROOT;
 			}
 
+			if ( $event->Name == 'OnLoginAs' ) {
+				return $this->_hasAdminSession();
+			}
+
 			if ( !$this->Application->isAdminUser ) {
 				$user_id = $this->Application->RecallVar('user_id');
 				$items_info = $this->Application->GetVar($event->getPrefixSpecial(true));
@@ -1761,4 +1788,21 @@
 			$event->SetRedirectParam('reset', 1);
 			$event->SetRedirectParam('pass', 'm');
 		}
+
+
+		/**
+		 * Login for front-end user when admin session is present
+		 *
+		 * @param kEvent $event
+		 * @return void
+		 * @access protected
+		 */
+		protected function OnLoginAs(&$event)
+		{
+
+			$user_helper =& $this->Application->recallObject('UserHelper');
+			/* @var $user_helper UserHelper */
+
+			$user_helper->loginUserById( $this->Application->GetVar('user') );
+		}
 	}