diff --git a/plugins/check_smtp.c b/plugins/check_smtp.c
index 324549d4..fd492294 100644
--- a/plugins/check_smtp.c
+++ b/plugins/check_smtp.c
@@ -697,6 +697,8 @@ check_smtp_config_wrapper process_arguments(int argc, char **argv) {
 			} else {
 				usage2(_("Invalid hostname/address"), argv[c]);
 			}
+		} else {
+			result.config.server_address = strdup("localhost");
 		}
 	}
 
diff --git a/plugins/check_smtp.d/config.h b/plugins/check_smtp.d/config.h
index c8660445..0a6511ef 100644
--- a/plugins/check_smtp.d/config.h
+++ b/plugins/check_smtp.d/config.h
@@ -52,7 +52,7 @@ typedef struct {
 check_smtp_config check_smtp_config_init() {
 	check_smtp_config tmp = {
 		.server_port = SMTP_PORT,
-		.server_address = strdup("localhost"),
+		.server_address = NULL,
 		.localhostname = NULL,
 
 		.server_expect = SMTP_EXPECT,