diff --git a/sql_global_addressbooks/config.inc.php.dist b/sql_global_addressbooks/config.inc.php.dist
index ad889f9..13c54db 100644
--- a/sql_global_addressbooks/config.inc.php.dist
+++ b/sql_global_addressbooks/config.inc.php.dist
@@ -6,6 +6,17 @@ All Configuration Options are Tabbed. Default Disabled Configuration starts '//'
 Any line being Commented Out or Removed is the Same as Leaving it at Default, or Disabled.
 So Remove Lines for any Books you do not wish to use to simplify this Configuration File. */
 
+/*
+Use these parameters to connect to an external database.
+If the database type value is empty (default), the roundcube database is used. */
+//	$config['_database_type'] = '';
+//	$config['_database_host'] = 'localhost';
+/* If the port value is empty (default), it's set by the database driver */
+//	$config['_database_port'] = '';
+//	$config['_database_user'] = 'roundcube';
+//	$config['_database_pass'] = '';
+//	$config['_database_name'] = 'roundcubemail';
+
 /*
 The `Domain Book` is an Address Book which will contain all the members which have the same
 e-mail domain as the logged in user themself, the only values for configuration are:
diff --git a/sql_global_addressbooks/sql_global_backend.php b/sql_global_addressbooks/sql_global_backend.php
index d267211..e3d6232 100644
--- a/sql_global_addressbooks/sql_global_backend.php
+++ b/sql_global_addressbooks/sql_global_backend.php
@@ -16,11 +16,26 @@ class sql_global_backend extends rcube_addressbook {
 	public $primary_key = 'ID';
 	public $readonly = true;
 
-	private $filter, $result, $name;
+	private $filter, $result, $name, $db;
 
 	public function __construct($name) {
 		$this->ready = true;
-		$this->name  = $name;
+		$this->name = $name;
+		$dbtype = rcmail::get_instance()->config->get('_database_type', '');
+		if (empty($dbtype)) {
+			// use roundcube native database
+			$this->db = rcube::get_instance()->db;
+		} else {
+			// setup connection to external database
+			$dbhost = rcmail::get_instance()->config->get('_database_host', '');
+			$dbport = rcmail::get_instance()->config->get('_database_port', '');
+			$dbuser = rcmail::get_instance()->config->get('_database_user', 'roundcube');
+			$dbpass = rcmail::get_instance()->config->get('_database_pass', '');
+			$dbname = rcmail::get_instance()->config->get('_database_name', 'roundcubemail');
+			if (!empty($dbport)) { $dbport = ':'.$dbport; }
+			$dsn = $dbtype.'://'.$dbuser.':'.$dbpass.'@'.$dbhost.$dbport.'/'.$dbname;
+			$this->db = rcube_db::factory($dsn);
+		}
 	}
 
 	public function get_name() { return $this->name; }
@@ -33,7 +48,7 @@ public function reset() {
 	}
 
 	public function get_record($id, $assoc=false) {
-		$db = rcube::get_instance()->db;
+		$db = $this->db;
 		$db->query('SELECT * FROM global_addressbook WHERE `ID`=?', $id);
 		if ($sql_arr = $db->fetch_assoc()) {
 			$sql_arr['email'] = explode(',', $sql_arr['email']);
@@ -47,36 +62,38 @@ public function get_record($id, $assoc=false) {
 
 	public function list_records($cols=null, $subset=0) {
 		$this->result = $this->count();
-		$db = rcube::get_instance()->db;
+		$db = $this->db;
 
 		if (empty($this->group_id)) {
 
 			switch ($this->name) {
-				case 'global':
-					$cf = rcmail::get_instance()->config->get('_sql_gb_data_allowed', array('*'));
-					$fc = rcmail::get_instance()->config->get('_sql_gb_data_hidden', array());
-					if ($cf === array('*')) {
-						$cf = array();
-					} else { $x[] = 'domain IN (' . $db->array2list($cf) . ')'; }
-					if ($this->filter)  { $x[] = '(' . $this->filter .')'; }
-					if (count($fc) > 0) { $x[] = 'domain NOT IN (' . $db->array2list($fc) . ')'; }
-					$x = count($x) > 0 ? (' WHERE ' . implode(' AND ', $x)):'';
-					$db->query('SELECT * FROM global_addressbook' . $x);
-					break;
-
-				case 'domain':
-					$x = $this->filter ? (' (' . $this->filter . ') AND '):' ';
-					$db->query('SELECT * FROM global_addressbook WHERE' . $x . 'domain=?', rcmail::get_instance()->user->get_username('domain'));
-					break;
-
-				default:
-					$d = rcmail::get_instance()->config->get('_sql_supportbook', array());
-					$f = array_flip(sql_global_addressbooks::ac($d, 0));
-					array_shift($z = $d[$f[$this->name]]);
-					if ($this->filter) { $x[] = '(' . $this->filter .')'; }
-					if (count($z) > 0) { $x[] = 'domain IN (' . $db->array2list($z) . ')'; }
-					$x = count($x)> 0 ? (' WHERE ' . implode(' AND ', $x)):'';
-					$db->query('SELECT * FROM global_addressbook' . $x);
+			case 'global':
+				$cf = rcmail::get_instance()->config->get('_sql_gb_data_allowed', array('*'));
+				$fc = rcmail::get_instance()->config->get('_sql_gb_data_hidden', array());
+				if ($cf === array('*')) {
+					$cf = array();
+				} else {
+					$x[] = 'domain IN (' . $db->array2list($cf) . ')';
+				}
+				if ($this->filter) { $x[] = '(' . $this->filter .')'; }
+				if (count($fc) > 0) { $x[] = 'domain NOT IN (' . $db->array2list($fc) . ')'; }
+				$x = count($x) > 0 ? (' WHERE ' . implode(' AND ', $x)):'';
+				$db->query('SELECT * FROM global_addressbook' . $x);
+				break;
+
+			case 'domain':
+				$x = $this->filter ? (' (' . $this->filter . ') AND '):' ';
+				$db->query('SELECT * FROM global_addressbook WHERE' . $x . 'domain=?', rcmail::get_instance()->user->get_username('domain'));
+				break;
+
+			default:
+				$d = rcmail::get_instance()->config->get('_sql_supportbook', array());
+				$f = array_flip(sql_global_addressbooks::ac($d, 0));
+				array_shift($z = $d[$f[$this->name]]);
+				if ($this->filter) { $x[] = '(' . $this->filter .')'; }
+				if (count($z) > 0) { $x[] = 'domain IN (' . $db->array2list($z) . ')'; }
+				$x = count($x)> 0 ? (' WHERE ' . implode(' AND ', $x)):'';
+				$db->query('SELECT * FROM global_addressbook' . $x);
 			}
 
 		} else {
@@ -86,9 +103,6 @@ public function list_records($cols=null, $subset=0) {
 
 		while ($ret = $db->fetch_assoc()) {
 			$ret['email'] = explode(',', $ret['email']);
-			//$names = explode(' ', $ret['name']);
-			//$ret['surname'] = array_push($names);
-			//$ret['firsname']= implode(' ', $names);
 			$this->result->add($ret);
 		}
 		return $this->result;
@@ -103,114 +117,105 @@ function list_groups($search = null, $mode=0) {
 
 		if ($search) {
 			switch (intval($mode)) {
-	            case 1:
-	                $x = $rc->db->ilike('domain', $search);
-	                break;
-	            case 2:
-	                $x = $rc->db->ilike('domain', $search . '%');
-	                break;
-	            default:
-	                $x = $rc->db->ilike('domain', '%' . $search . '%');
-            }
-            $x = ' WHERE ' . $x . ' ';
+			case 1:
+				$x = $db->ilike('domain', $search);
+				break;
+			case 2:
+				$x = $db->ilike('domain', $search . '%');
+				break;
+			default:
+				$x = $db->ilike('domain', '%' . $search . '%');
+			}
+			$x = ' WHERE ' . $x . ' ';
 		} else { $x = ' '; }
 
 		if ($cf === array('*')) {
 			$cf = array();
-			$rc->db->query('SELECT domain FROM global_addressbook' . $x . 'GROUP BY domain');
-			while ($ret = $rc->db->fetch_assoc()) {$cf[] = $ret['domain']; }
+			$db->query('SELECT domain FROM global_addressbook' . $x . 'GROUP BY domain');
+			while ($ret = $db->fetch_assoc()) {$cf[] = $ret['domain']; }
 		}
 
 		$co = array();
 		foreach (array_diff($cf, $fc) as $v) { $co[] = array('ID' => $v, 'name' => $v); }
-        //file_put_contents('/var/www/test.log', print_r([$co, $search, $mode, $this->groups, $this->name, $this->group_id], true));
 		return $co;
 
 	}
 
 	public function search($fields, $value, $strict=false, $select=true, $nocount=false, $required=array()) {
 		if (!is_array($fields)) { $fields = array($fields); }
-        if (!is_array($required) && !empty($required)) { $required = array($required); }
-
-
-        $db = rcube::get_instance()->db;
-        $where = array();
-        $mode = intval($mode);
-        $WS = ' ';
-
-        foreach ($fields as $idx => $col) {
-
-        	if ($col == 'ID' || $col == $this->primary_key) {
-    			$ids     = !is_array($value) ? explode(',', $value) : $value;
-                $ids     = $db->array2list($ids, 'integer');
-                $where[] = 'c.' . $this->primary_key.' IN ('.$ids.')';
-                continue;
-            } else if ($col == '*') {
-        			$words = array();
-        			foreach (explode($WS, rcube_utils::normalize_string($value)) as $word) {
-        				switch ($mode) {
-        					case 1: // Strict
-        						$words[]='(' . $db->ilike('name', $word . '%')
-		                            . ' OR ' . $db->ilike('email',$word . '%')
-		                            . ' OR ' . $db->ilike('name', '%' . $WS . $word . $WS . '%')
-		                            . ' OR ' . $db->ilike('email','%' . $WS . $word . $WS . '%')
-		                            . ' OR ' . $db->ilike('name', '%' . $WS . $word)
-		                            . ' OR ' . $db->ilike('email','%' . $WS . $word). ')';
-        						break;
-
-        					case 2: // Prefix
-        						$words[]='(' . $db->ilike('name', $word . '%')
-                            		. ' OR ' . $db->ilike('email',$word . '%')
-                            		. ' OR ' . $db->ilike('name', '%' . $WS . $word . '%')
-                            		. ' OR ' . $db->ilike('email','%' . $WS . $word . '%') . ')';
-								break;
-
-        					default: // Partial
-        						$words[]='(' . $db->ilike('name', '%' . $word . '%')
-        						    . ' OR ' . $db->ilike('email','%' . $word . '%') . ')';
-        						break;
-        				}
-        			}
-        			$where[] = '(' . join(' AND ', $words) . ')';
-        	//} else {
-        	} elseif ($col !== 'firstname' && $col !== 'surname') {
-        		$val = is_array($value) ? $value[$idx] : $value;
-
-        		switch ($mode) {
-                    case 1: // strict
-                        $where[] = '(' . $db->quote_identifier($col) . ' = ' . $db->quote($val)
-                            . ' OR ' . $db->ilike($col, $val . $AS . '%')
-                            . ' OR ' . $db->ilike($col, '%' . $AS . $val . $AS . '%')
-                            . ' OR ' . $db->ilike($col, '%' . $AS . $val) . ')';
-                        break;
-                    case 2: // prefix
-                        $where[] = '(' . $db->ilike($col, $val . '%')
-                            . ' OR ' . $db->ilike($col, $AS . $val . '%') . ')';
-                        break;
-                    default: // partial
-                        $where[] = $db->ilike($col, '%' . $val . '%');
-                }
-        	}
-
-	        if (!empty($where)) {
-	            $this->set_search_set(join(is_array($value) ? ' AND ' : ' OR ', $where));
-	            /*if ($select) {
-	                $this->list_records(null, 0, $nocount);
-	            } else { $this->result = $this->count(); */
-	        }
-
-        }
+		if (!is_array($required) && !empty($required)) { $required = array($required); }
+
+		$db = $this->db;
+		$where = array();
+		$mode = intval($mode);
+		$WS = ' ';
+
+		foreach ($fields as $idx => $col) {
+
+			if ($col == 'ID' || $col == $this->primary_key) {
+				$ids = !is_array($value) ? explode(',', $value) : $value;
+				$ids = $db->array2list($ids, 'integer');
+				$where[] = 'c.' . $this->primary_key.' IN ('.$ids.')';
+				continue;
+			} else if ($col == '*') {
+				$words = array();
+				foreach (explode($WS, rcube_utils::normalize_string($value)) as $word) {
+					switch ($mode) {
+					case 1: // strict
+						$words[]='(' . $db->ilike('name', $word . '%')
+							. ' OR ' . $db->ilike('email',$word . '%')
+							. ' OR ' . $db->ilike('name', '%' . $WS . $word . $WS . '%')
+							. ' OR ' . $db->ilike('email','%' . $WS . $word . $WS . '%')
+							. ' OR ' . $db->ilike('name', '%' . $WS . $word)
+							. ' OR ' . $db->ilike('email','%' . $WS . $word). ')';
+						break;
+
+					case 2: // prefix
+						$words[]='(' . $db->ilike('name', $word . '%')
+							. ' OR ' . $db->ilike('email',$word . '%')
+							. ' OR ' . $db->ilike('name', '%' . $WS . $word . '%')
+							. ' OR ' . $db->ilike('email','%' . $WS . $word . '%') . ')';
+						break;
+
+					default: // partial
+						$words[]='(' . $db->ilike('name', '%' . $word . '%')
+							. ' OR ' . $db->ilike('email','%' . $word . '%') . ')';
+						break;
+					}
+				}
+				$where[] = '(' . join(' AND ', $words) . ')';
+			} elseif ($col !== 'firstname' && $col !== 'surname') {
+				$val = is_array($value) ? $value[$idx] : $value;
+
+				switch ($mode) {
+				case 1: // strict
+					$where[] = '(' . $db->quote_identifier($col) . ' = ' . $db->quote($val)
+						. ' OR ' . $db->ilike($col, $val . $AS . '%')
+						. ' OR ' . $db->ilike($col, '%' . $AS . $val . $AS . '%')
+						. ' OR ' . $db->ilike($col, '%' . $AS . $val) . ')';
+					break;
+				case 2: // prefix
+					$where[] = '(' . $db->ilike($col, $val . '%')
+						. ' OR ' . $db->ilike($col, $AS . $val . '%') . ')';
+					break;
+				default: // partial
+					$where[] = $db->ilike($col, '%' . $val . '%');
+				}
+			}
 
+			if (!empty($where)) {
+				$this->set_search_set(join(is_array($value) ? ' AND ' : ' OR ', $where));
+			}
+
+		}
 
 		return $this->list_records();
 	}
+
 	function get_group($group_id) { return $this->groups ? array('ID' => $group_id, 'name' => $group_id) : null; }
 	public function count() { return new rcube_result_set(1, ($this->list_page-1) * $this->page_size); }
 	public function get_result() { return $this->result; }
-	public function set_group($gid) {
-        $this->group_id = $gid;
-        $this->cache = null;
-    }
+	public function set_group($gid) { $this->group_id = $gid; $this->cache = null; }
 	function create_group($name) { return false; }
 	function delete_group($gid) { return false; }
 	function rename_group($gid, $newname) { return $newname; }