Had to activate the following modules in SquirrelMail: server_settings_backend server_side_filters server_side_filters_maildrop In the sqmail/config/config.php file we must have the following settings: $default_folder_prefix = ‘INBOX’; $trash_folder = ‘.Trash’; $sent_folder = ‘.Sent’; $draft_folder = ‘.Drafts’; Especially important is the $default_folder_prefix, which is removed