diff -urNp -x '*.orig' postfix-3.8.1.org/src/global/mail_params.c postfix-3.8.1/src/global/mail_params.c
--- postfix-3.8.1.org/src/global/mail_params.c	2021-10-22 20:47:31.000000000 +0200
+++ postfix-3.8.1/src/global/mail_params.c	2023-07-09 22:19:21.172026512 +0200
@@ -83,6 +83,7 @@
 /*	char	*var_debug_peer_list;
 /*	int	var_debug_peer_level;
 /*	int	var_in_flow_delay;
+/*	char	*var_reject_reply_msg_access_denied;
 /*	int	var_fault_inj_code;
 /*	char   *var_bounce_service;
 /*	char   *var_cleanup_service;
@@ -319,6 +320,7 @@ char   *var_import_environ;
 char   *var_export_environ;
 char   *var_debug_peer_list;
 int     var_debug_peer_level;
+char	*var_reject_reply_msg_access_denied;
 int     var_fault_inj_code;
 char   *var_bounce_service;
 char   *var_cleanup_service;
@@ -806,6 +808,7 @@ void    mail_params_init()
 	VAR_SMTPUTF8_AUTOCLASS, DEF_SMTPUTF8_AUTOCLASS, &var_smtputf8_autoclass, 1, 0,
 	VAR_DROP_HDRS, DEF_DROP_HDRS, &var_drop_hdrs, 0, 0,
 	VAR_INFO_LOG_ADDR_FORM, DEF_INFO_LOG_ADDR_FORM, &var_info_log_addr_form, 1, 0,
+	VAR_REJECT_REPLY_MSG_ACCESS_DENIED, DEF_REJECT_REPLY_MSG_ACCESS_DENIED, &var_reject_reply_msg_access_denied, 1, 0,
 	0,
     };
     static const CONFIG_STR_FN_TABLE function_str_defaults_2[] = {
diff -urNp -x '*.orig' postfix-3.8.1.org/src/global/mail_params.h postfix-3.8.1/src/global/mail_params.h
--- postfix-3.8.1.org/src/global/mail_params.h	2023-07-09 22:19:21.003024104 +0200
+++ postfix-3.8.1/src/global/mail_params.h	2023-07-09 22:19:21.172026512 +0200
@@ -4411,6 +4411,13 @@ extern bool var_ign_srv_lookup_err;
 #define DEF_ALLOW_SRV_FALLBACK	0
 extern bool var_allow_srv_fallback;
 
+ /*
+  * SMTPD messages
+  */
+#define VAR_REJECT_REPLY_MSG_ACCESS_DENIED	"smtpd_reject_msg_access_denied"
+#define DEF_REJECT_REPLY_MSG_ACCESS_DENIED	"rejected: Relay access denied."
+extern char *var_reject_reply_msg_access_denied;
+
 /* LICENSE
 /* .ad
 /* .fi
diff -urNp -x '*.orig' postfix-3.8.1.org/src/smtpd/smtpd.c postfix-3.8.1/src/smtpd/smtpd.c
--- postfix-3.8.1.org/src/smtpd/smtpd.c	2023-06-05 21:06:51.000000000 +0200
+++ postfix-3.8.1/src/smtpd/smtpd.c	2023-07-09 22:19:21.173026526 +0200
@@ -6645,6 +6645,7 @@ int     main(int argc, char **argv)
 	VAR_MILT_MACRO_DEFLTS, DEF_MILT_MACRO_DEFLTS, &var_milt_macro_deflts, 0, 0,
 	VAR_SMTPD_MILTER_MAPS, DEF_SMTPD_MILTER_MAPS, &var_smtpd_milter_maps, 0, 0,
 	VAR_STRESS, DEF_STRESS, &var_stress, 0, 0,
+	VAR_REJECT_REPLY_MSG_ACCESS_DENIED, DEF_REJECT_REPLY_MSG_ACCESS_DENIED, &var_reject_reply_msg_access_denied, 1, 0,
 	VAR_UNV_FROM_WHY, DEF_UNV_FROM_WHY, &var_unv_from_why, 0, 0,
 	VAR_UNV_RCPT_WHY, DEF_UNV_RCPT_WHY, &var_unv_rcpt_why, 0, 0,
 	VAR_REJECT_TMPF_ACT, DEF_REJECT_TMPF_ACT, &var_reject_tmpf_act, 1, 0,