--- mandrill/mandrill.admin.inc	Wed Oct 10 06:00:10 2012
+++ mandrill/mandrill.admin.inc	Tue Oct 23 14:03:33 2012
@@ -135,17 +135,26 @@
 
   switch ($form_state['values']['mandrill_status']) {
     case MANDRILL_STATUS_ON:
-      variable_set('mail_system', array('default-system' => 'MandrillMailSystem'));
+      $mail_system = variable_get('mail_system', array('default-system' => 'DefaultMailSystem'));
+      $mail_system['default-system'] == 'MandrillMailSystem';
+      variable_set('mail_system', $mail_system);
       drupal_set_message(t('Mandrill will be used to deliver all site emails.'));
       watchdog('mandrill', 'Mandrill has been enabled.');
       break;
     case MANDRILL_STATUS_TEST:
-      variable_set('mail_system', array('default-system' => 'TestingMandrillMailSystem'));
+      $mail_system = variable_get('mail_system', array('default-system' => 'DefaultMailSystem'));
+      $mail_system['default-system'] == 'TestingMandrillMailSystem';
+      variable_set('mail_system', $mail_system);
       drupal_set_message(t('Mandrill will be used in test mode. Emails will not actually be sent, just logged.'));
       watchdog('mandrill', 'Mandrill has been placed in test mode.');
       break;
     case MANDRILL_STATUS_OFF:
-      variable_set('mail_system', array('default-system' => 'DefaultMailSystem'));
+      $mail_system = variable_get('mail_system', array('default-system' => 'DefaultMailSystem'));
+      if ($mail_system['default-system'] == 'MandrillMailSystem'
+      or $mail_system['default-system'] == 'TestingMandrillMailSystem') {
+        $mail_system['default-system'] == 'DefaultMailSystem';
+        variable_set('mail_system', $mail_system);
+      }
       drupal_set_message(t('The default mail system will be used to deliver all site emails.'));
       watchdog('mandrill', 'Mandrill has been disabled.');
       break;
--- mandrill/mandrill.install	Wed Oct 10 06:00:10 2012
+++ mandrill/mandrill.install	Tue Oct 23 14:00:08 2012
@@ -18,6 +18,11 @@
  */
 function mandrill_disable() {
   // reset to default mail system
-  variable_set('mail_system', array('default-system' => 'DefaultMailSystem'));
+  $mail_system = variable_get('mail_system', array('default-system' => 'DefaultMailSystem'));
+  if ($mail_system['default-system'] == 'MandrillMailSystem'
+  or $mail_system['default-system'] == 'TestingMandrillMailSystem') {
+    $mail_system['default-system'] == 'DefaultMailSystem';
+    variable_set('mail_system', $mail_system);
+  }
   watchdog('mandrill', 'Mandrill has been disabled.');
 }