diff -Nur sendmail-8.11.0.orig/sendmail/conf.c sendmail-8.11.0/sendmail/conf.c
--- sendmail-8.11.0.orig/sendmail/conf.c	Sat Jul 15 19:35:18 2000
+++ sendmail-8.11.0/sendmail/conf.c	Sat Dec 23 00:58:26 2000
@@ -311,6 +311,8 @@
 	ColonOkInAddr = TRUE;
 	DontLockReadFiles = TRUE;
 	DoubleBounceAddr = "postmaster";
+	DetectTelnet = FALSE;
+	ExitOnTelnet = TRUE;
 	MaxHeadersLength = MAXHDRSLEN;
 	MaxForwardEntries = 0;
 #if SASL
diff -Nur sendmail-8.11.0.orig/sendmail/err.c sendmail-8.11.0/sendmail/err.c
--- sendmail-8.11.0.orig/sendmail/err.c	Fri May 26 02:08:29 2000
+++ sendmail-8.11.0/sendmail/err.c	Sat Dec 23 01:00:25 2000
@@ -786,15 +786,15 @@
 		(void) snprintf(eb, spaceleft, "%s... ",
 			shortenstring(to, MAXSHORTSTR));
 		spaceleft -= strlen(eb);
-		while (*eb != '\0')
-			*eb++ &= 0177;
+/*		while (*eb != '\0')
+			*eb++ &= 0177; */
 	}
 
 	/* output the message */
 	(void) vsnprintf(eb, spaceleft, fmt, ap);
 	spaceleft -= strlen(eb);
-	while (*eb != '\0')
-		*eb++ &= 0177;
+/*	while (*eb != '\0')
+		*eb++ &= 0177; */
 
 	/* output the error code, if any */
 	if (eno != 0)
diff -Nur sendmail-8.11.0.orig/sendmail/readcf.c sendmail-8.11.0/sendmail/readcf.c
--- sendmail-8.11.0.orig/sendmail/readcf.c	Wed Jul 12 18:44:09 2000
+++ sendmail-8.11.0/sendmail/readcf.c	Sat Dec 23 01:08:28 2000
@@ -1709,6 +1709,10 @@
 # endif /* _FFR_TLS_1 */
 # define O_RANDFILE	0xc1
 	{ "RandFile",			O_RANDFILE,	OI_NONE	},
+#define O_DETECTTELNET	0xc2
+	{ "DetectTelnet",		O_DETECTTELNET,	OI_NONE },
+#define O_EXITONTELNET	0xc3
+	{ "ExitOnTelnet",		O_EXITONTELNET,	OI_NONE },
 	{ NULL,				'\0',		OI_NONE	}
 };
 
@@ -2943,6 +2947,14 @@
 		QueueFileMode = atooct(val) & 0777;
 		break;
 #endif /* _FFR_QUEUE_FILE_MODE */
+
+	  case O_DETECTTELNET:	/* detect telnet */
+		DetectTelnet = atobool(val);
+		break;
+
+	  case O_EXITONTELNET:	/* exit if telnet detected */
+		ExitOnTelnet = atobool(val);
+		break;
 
 	  default:
 		if (tTd(37, 1))
diff -Nur sendmail-8.11.0.orig/sendmail/sendmail.h sendmail-8.11.0/sendmail/sendmail.h
--- sendmail-8.11.0.orig/sendmail/sendmail.h	Tue Jul 18 04:24:47 2000
+++ sendmail-8.11.0/sendmail/sendmail.h	Sat Dec 23 01:12:30 2000
@@ -1682,6 +1682,8 @@
 EXTERN bool	UseErrorsTo;	/* use Errors-To: header (back compat) */
 EXTERN bool	UseHesiod;	/* using Hesiod -- interpret Hesiod errors */
 EXTERN bool	UseNameServer;	/* using DNS -- interpret h_errno & MX RRs */
+EXTERN bool	DetectTelnet;	/* force telnet detection on/off */
+EXTERN bool	ExitOnTelnet;	/* exit if telnet detected */
 EXTERN char	InetMode;		/* default network for daemon mode */
 EXTERN char	OpMode;		/* operation mode, see below */
 EXTERN char	SpaceSub;	/* substitution for <lwsp> */
diff -Nur sendmail-8.11.0.orig/sendmail/srvrsmtp.c sendmail-8.11.0/sendmail/srvrsmtp.c
--- sendmail-8.11.0.orig/sendmail/srvrsmtp.c	Wed Jul 19 22:21:35 2000
+++ sendmail-8.11.0/sendmail/srvrsmtp.c	Sat Dec 23 01:41:30 2000
@@ -13,6 +13,7 @@
 
 
 #include <sendmail.h>
+#include <arpa/telnet.h>
 
 #ifndef lint
 # if SMTP
@@ -207,6 +208,9 @@
 	char *args[MAXSMTPARGS];
 	char inp[MAXLINE];
 	char cmdbuf[MAXLINE];
+	char telnet_request[] = {IAC, DO, TELOPT_SGA, 0};
+	char telnet_response[] = {IAC, WILL, TELOPT_SGA, 0};
+	char *telnet_tmp;
 # if SASL
 	sasl_conn_t *conn;
 	volatile bool sasl_ok;
@@ -429,12 +433,8 @@
 	id = strchr(inp, ' ');
 	if (id == NULL)
 		id = &inp[strlen(inp)];
-	if (p == NULL)
-		snprintf(cmdbuf, sizeof cmdbuf,
-			 "%s %%.*s ESMTP%%s", greetcode);
-	else
-		snprintf(cmdbuf, sizeof cmdbuf,
-			 "%s-%%.*s ESMTP%%s", greetcode);
+	snprintf(cmdbuf,sizeof cmdbuf,"%s%c%%.*s ESMTP%%s%s", greetcode,
+		(p == NULL)? ' ' : '-', DetectTelnet ? telnet_request : "");
 	message(cmdbuf, id - inp, inp, id);
 
 	/* output remaining lines */
@@ -520,6 +520,20 @@
 				e->e_sendqueue = NULL;
 			goto doquit;
 		}
+
+		if (DetectTelnet && strlen(inp) >= 3)
+			for (telnet_tmp = inp; *(telnet_tmp+2); telnet_tmp++)
+				if (!strncmp(telnet_tmp, telnet_response, 3))
+				{
+					sm_syslog(LOG_NOTICE, e->e_id,
+					  "telnet detected from %.100s (%.100s)",
+					  CurSmtpClient, anynet_ntoa(&RealHostAddr));
+					if (ExitOnTelnet)
+					{
+						message("571 Unauthorized usage prohibited");
+						goto doquit;
+					}
+				}
 
 		/* clean up end of line */
 		fixcrlf(inp, TRUE);