diff -urN ../exim-4.95.orig/src/globals.c ./src/globals.c
--- ../exim-4.95.orig/src/globals.c	2021-09-28 11:24:46.000000000 +0300
+++ ./src/globals.c	2022-01-26 19:02:38.369397000 +0200
@@ -1499,7 +1499,8 @@
 int     smtp_mailcmd_max       = -1;
 FILE   *smtp_out               = NULL;
 uschar *smtp_etrn_command      = NULL;
-int     smtp_max_synprot_errors= 3;
+//int     smtp_max_synprot_errors= 3;
+uschar *smtp_max_synprot_errors = NULL;
 int     smtp_max_unknown_commands = 3;
 uschar *smtp_notquit_reason    = NULL;
 unsigned smtp_peer_options     = 0;
diff -urN ../exim-4.95.orig/src/globals.h ./src/globals.h
--- ../exim-4.95.orig/src/globals.h	2021-09-28 11:24:46.000000000 +0300
+++ ./src/globals.h	2022-01-26 19:03:58.478267000 +0200
@@ -971,7 +971,8 @@
 extern int     smtp_load_reserve;      /* Only from reserved if load > this */
 extern int     smtp_mailcmd_count;     /* Count of MAIL commands */
 extern int     smtp_mailcmd_max;       /* Limit for MAIL commands */
-extern int     smtp_max_synprot_errors;/* Max syntax/protocol errors */
+//extern int     smtp_max_synprot_errors;/* Max syntax/protocol errors */
+extern uschar *smtp_max_synprot_errors; /* Max syntax/protocol errors */
 extern int     smtp_max_unknown_commands; /* As it says */
 extern uschar *smtp_names[];	       /* decode for command codes */
 extern uschar *smtp_notquit_reason;    /* Global for disconnect reason */
diff -urN ../exim-4.95.orig/src/readconf.c ./src/readconf.c
--- ../exim-4.95.orig/src/readconf.c	2021-09-28 11:24:46.000000000 +0300
+++ ./src/readconf.c	2022-01-28 00:48:18.536119000 +0200
@@ -324,7 +324,7 @@
   { "smtp_etrn_command",        opt_stringptr,   {&smtp_etrn_command} },
   { "smtp_etrn_serialize",      opt_bool,        {&smtp_etrn_serialize} },
   { "smtp_load_reserve",        opt_fixed,       {&smtp_load_reserve} },
-  { "smtp_max_synprot_errors",  opt_int,         {&smtp_max_synprot_errors} },
+  { "smtp_max_synprot_errors",  opt_stringptr,   {&smtp_max_synprot_errors} },
   { "smtp_max_unknown_commands",opt_int,         {&smtp_max_unknown_commands} },
   { "smtp_ratelimit_hosts",     opt_stringptr,   {&smtp_ratelimit_hosts} },
   { "smtp_ratelimit_mail",      opt_stringptr,   {&smtp_ratelimit_mail} },
diff -urN ../exim-4.95.orig/src/smtp_in.c ./src/smtp_in.c
--- ../exim-4.95.orig/src/smtp_in.c	2021-09-28 11:24:46.000000000 +0300
+++ ./src/smtp_in.c	2022-01-26 19:03:06.370672000 +0200
@@ -3134,8 +3134,39 @@
   type == L_smtp_syntax_error ? "syntax" : "protocol",
   string_printing(smtp_cmd_buffer), host_and_ident(TRUE), errmess);
 
-if (++synprot_error_count > smtp_max_synprot_errors)
+
+#define DEFAULT_MAX_SYNPROT_ERRORS 3
+int max_synprot_errors = -1;
+if (smtp_max_synprot_errors != NULL)
   {
+  uschar *expanded = expand_string(smtp_max_synprot_errors);
+  if (expanded == NULL)
+    {
+    if (!f.expand_string_forcedfail)
+      log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_max_synprot_errors "
+        "failed for message from %s: %s; fallback to default value %d", host_and_ident(FALSE), expand_string_message, DEFAULT_MAX_SYNPROT_ERRORS);
+    }
+  /* For speed, interpret a decimal number inline here */
+  else
+    {
+    max_synprot_errors = 0;
+    uschar *s = expanded;
+    while (isdigit(*s))
+      max_synprot_errors = max_synprot_errors * 10 + *s++ - '0';
+    if (*s != 0)
+      {
+        log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_max_synprot_errors "
+          "for message from %s contains non-digit: %s; fallback to default value %d", host_and_ident(FALSE), expanded, DEFAULT_MAX_SYNPROT_ERRORS);
+        max_synprot_errors = DEFAULT_MAX_SYNPROT_ERRORS;
+      }
+    }
+  }
+if (max_synprot_errors == -1) max_synprot_errors = DEFAULT_MAX_SYNPROT_ERRORS;
+
+
+//if (++synprot_error_count > smtp_max_synprot_errors)
+if (++synprot_error_count > max_synprot_errors)
+  {
   yield = 1;
   log_write(0, LOG_MAIN|LOG_REJECT, "SMTP call from %s dropped: too many "
     "syntax or protocol errors (last command was \"%s\", %s)",
@@ -4236,7 +4267,38 @@
 	  *smtp_cmd_argument == 0 ? US"(no argument given)" :
 			     string_printing(smtp_cmd_argument));
 
-	if (++synprot_error_count > smtp_max_synprot_errors)
+
+#define DEFAULT_MAX_SYNPROT_ERRORS 3
+int max_synprot_errors = -1;
+if (smtp_max_synprot_errors != NULL)
+  {
+  uschar *expanded = expand_string(smtp_max_synprot_errors);
+  if (expanded == NULL)
+    {
+    if (!f.expand_string_forcedfail)
+      log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_max_synprot_errors "
+        "failed for message from %s: %s; fallback to default value %d", host_and_ident(FALSE), expand_string_message, DEFAULT_MAX_SYNPROT_ERRORS);
+    }
+  /* For speed, interpret a decimal number inline here */
+  else
+    {
+    max_synprot_errors = 0;
+    uschar *s = expanded;
+    while (isdigit(*s))
+      max_synprot_errors = max_synprot_errors * 10 + *s++ - '0';
+    if (*s != 0)
+      {
+        log_write(0, LOG_MAIN|LOG_PANIC, "expansion of smtp_max_synprot_errors "
+          "for message from %s contains non-digit: %s; fallback to default value %d", host_and_ident(FALSE), expanded, DEFAULT_MAX_SYNPROT_ERRORS);
+        max_synprot_errors = DEFAULT_MAX_SYNPROT_ERRORS;
+      }
+    }
+  }
+if (max_synprot_errors == -1) max_synprot_errors = DEFAULT_MAX_SYNPROT_ERRORS;
+
+
+//	if (++synprot_error_count > smtp_max_synprot_errors)
+	if (++synprot_error_count > max_synprot_errors)
 	  {
 	  log_write(0, LOG_MAIN|LOG_REJECT, "SMTP call from %s dropped: too many "
 	    "syntax or protocol errors (last command was \"%s\", %s)",