diff --git a/CHANGELOG.md b/CHANGELOG.md
index a25f32954..9c458403b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Store uploads metadata in a separate sql database table instead of a session (#8415)
 - Mouse-over menu on messages list (#7141)
 - Advanced mail search syntax with more possibilities (without UI) (#8502)
+- Added an option for a default mail search scope (#9077, #7556)
 - Support for HAproxy protocol header in IMAP connections (#8625)
 - Change 'smtp_log' option default value to False
 - Delete messages directly from Junk on folder purge if delete_junk is enabled (#8766)
diff --git a/config/defaults.inc.php b/config/defaults.inc.php
index 43a38750e..d6ac40850 100644
--- a/config/defaults.inc.php
+++ b/config/defaults.inc.php
@@ -1434,13 +1434,18 @@ $config['force_7bit'] = false;
 // The entry with key '*' stands for all folders which do not have a specific list set.
 // Supported fields: subject, from, to, cc, bcc, replyto, followupto, body, text.
 // Please note that folder names should to be in sync with $config['*_mbox'] options
-$config['search_mods'] = null;  // Example: ['*' => ['subject'=>1, 'from'=>1], 'Sent' => ['subject'=>1, 'to'=>1]];
+// Example: ['*' => ['subject'=>1, 'from'=>1], 'Sent' => ['subject'=>1, 'to'=>1]];
+$config['search_mods'] = null;
 
-// Default search scope
-$config['search_scope'] = null; // Example: 'all' - for all folders, 'base' - for current folder, 'sub' - for this and subfolders
+// Default search scope. Supported values:
+// 'base' - for current folder (default),
+// 'sub' - for current folder and subfolders,
+// 'all' - for all folders
+$config['search_scope'] = null;
 
 // Defaults of the addressbook search field configuration.
-$config['addressbook_search_mods'] = null;  // Example: ['name'=>1, 'firstname'=>1, 'surname'=>1, 'email'=>1, '*'=>1];
+// Example: ['name'=>1, 'firstname'=>1, 'surname'=>1, 'email'=>1, '*'=>1];
+$config['addressbook_search_mods'] = null;
 
 // Directly delete messages in Junk instead of moving to Trash
 $config['delete_junk'] = false;
diff --git a/program/actions/mail/index.php b/program/actions/mail/index.php
index 6c1f69dac..26a8bf09b 100644
--- a/program/actions/mail/index.php
+++ b/program/actions/mail/index.php
@@ -97,16 +97,7 @@ class rcmail_action_mail_index extends rcmail_action
 
             if (empty($rcmail->action)) {
                 $rcmail->output->set_env('search_mods', self::search_mods());
-
-                $scope = rcube_utils::get_input_string('_scope', rcube_utils::INPUT_GET);
-                if (!$scope && isset($_SESSION['search_scope']) && $rcmail->output->get_env('search_request')) {
-                    $scope = $_SESSION['search_scope'];
-                }
-
-                if (!$scope) {
-                    $scope = self::search_scope();
-                }
-                $rcmail->output->set_env('search_scope', strtolower($scope));
+                $rcmail->output->set_env('search_scope', self::search_scope());
 
                 self::list_pagetitle();
             }
@@ -278,18 +269,26 @@ class rcmail_action_mail_index extends rcmail_action
     }
 
     /**
-    * Returns default search scopes
-    */
+     * Returns a requested or default search scope
+     */
     public static function search_scope()
     {
         $rcmail = rcmail::get_instance();
-        $scope = $rcmail->config->get('search_scope');
+        $scope = rcube_utils::get_input_string('_scope', rcube_utils::INPUT_GET);
 
-        if (empty($scope)) {
+        if (!$scope && isset($_SESSION['search_scope']) && $rcmail->output->get_env('search_request')) {
+            $scope = $_SESSION['search_scope'];
+        }
+
+        if (!$scope) {
+            $scope = $rcmail->config->get('search_scope');
+        }
+
+        if (!$scope || !preg_match('/^(all|sub|base)$/i', $scope)) {
             $scope = 'base';
         }
 
-        return $scope;
+        return strtolower($scope);
     }
 
     /**