diff --git a/install/lib/installer_base.lib.php b/install/lib/installer_base.lib.php
index 22f9c7838896c71d2c4435af07e5b447e646631a..dfd0842568b19d12b249c4befe590ffe67600cdd 100644
--- a/install/lib/installer_base.lib.php
+++ b/install/lib/installer_base.lib.php
@@ -391,6 +391,9 @@ class installer_base {
 			}
 		}
 
+		// preserve needed values in $conf  (should just array_merge $tpl_ini_array into $conf?)
+		$conf['mail']['content_filter'] = $tpl_ini_array['mail']['content_filter'];
+
 		$server_ini_content = array_to_ini($tpl_ini_array);
 
 		$mail_server_enabled = ($conf['services']['mail'])?1:0;
@@ -1475,7 +1478,7 @@ class installer_base {
 			}
 			$new_options[] = $value;
 		}
-		if ($configure_lmtp) {
+		if ($configure_lmtp && $conf['mail']['content_filter'] === 'amavisd') {
 			for ($i = 0; isset($new_options[$i]); $i++) {
 				if ($new_options[$i] == 'reject_unlisted_recipient') {
 					array_splice($new_options, $i+1, 0, array("check_recipient_access proxy:mysql:${quoted_config_dir}/mysql-verify_recipients.cf"));
diff --git a/server/plugins-available/postfix_server_plugin.inc.php b/server/plugins-available/postfix_server_plugin.inc.php
index 2d6f063cd855752aa730a5bda6c34961949a00e2..34a8509e4f0c90b48b4fa8af7517df6997050d71 100644
--- a/server/plugins-available/postfix_server_plugin.inc.php
+++ b/server/plugins-available/postfix_server_plugin.inc.php
@@ -326,7 +326,7 @@ class postfix_server_plugin {
 			}
 			$new_options[] = $value;
 		}
-		if (defined($configure_lmtp) && $configure_lmtp) {
+		if (defined($configure_lmtp) && $configure_lmtp && $mail_config['content_filter'] == 'amavisd') {
 			for ($i = 0; isset($new_options[$i]); $i++) {
 				if ($new_options[$i] == 'reject_unlisted_recipient') {
 					array_splice($new_options, $i+1, 0, array("check_recipient_access proxy:mysql:${quoted_postfix_config_dir}/mysql-verify_recipients.cf"));