diff -urN ../roundcubemail-1.4.3.orig/program/include/rcmail_sendmail.php ./program/include/rcmail_sendmail.php
--- ../roundcubemail-1.4.3.orig/program/include/rcmail_sendmail.php	2020-02-19 22:55:57.000000000 +0200
+++ ./program/include/rcmail_sendmail.php	2020-05-10 18:00:30.266611000 +0300
@@ -892,7 +892,9 @@
                 && !$this->rcmail->config->get('sig_below')
                 && ($this->data['mode'] == self::MODE_REPLY || $this->data['mode'] == self::MODE_FORWARD);
 
-            $separator     = $top_posting ? '---' : '-- ';
+//            $separator     = $top_posting ? '---' : '-- ';
+            $separator = ($top_posting ? $this->rcmail->config->get('sig_separator_top_posting') : $this->rcmail->config->get('sig_separator_bottom_posting'));
+            if (!$separator) $separator = $top_posting ? '---' : '-- ';
             $add_separator = (bool) $this->rcmail->config->get('sig_separator');
 
             $field_attrib['onchange'] = rcmail_output::JS_OBJECT_NAME . ".change_identity(this)";