diff --git a/core/domains/domain_edit.php b/core/domains/domain_edit.php
index ea6283a487..ba00f1f0cc 100644
--- a/core/domains/domain_edit.php
+++ b/core/domains/domain_edit.php
@@ -105,6 +105,21 @@
 			$msg = '';
 			if (empty($domain_name)) { $msg .= $text['message-required'].$text['label-name']."<br>\n"; }
 			//if (empty($domain_description)) { $msg .= $text['message-required'].$text['label-description']."<br>\n"; }
+
+		//check for a duplicate domain name
+			if ($action == 'add') {
+				$sql = "select count(*) from v_domains ";
+				$sql .= "where domain_name = :domain_name ";
+				$sql .= "and destination_type = 'inbound' ";
+				$parameters['domain_name'] = $domain_name;
+				$num_rows = $database->select($sql, $parameters, 'column');
+				if ($num_rows > 0) {
+					$msg .= $text['message-duplicate']."<br>\n";
+				}
+				unset($sql, $parameters, $num_rows);
+			}
+
+		//show the message if it's not empty
 			if (!empty($msg) && empty($_POST["persistformvar"])) {
 				require_once "resources/header.php";
 				require_once "resources/persist_form_var.php";