By the way, I'd already had the POSIX compliant non-portable version
(pasted below.)  I posted the other one because of what I was told about
"portability".  When you guys agree on what should be done (at least in
this case) I would appreciate it if you let me know.


Index: extern.h
===================================================================
RCS file: /cvs/src/usr.bin/mail/extern.h,v
diff -u -p -r1.30 extern.h
--- extern.h	21 May 2024 05:00:48 -0000	1.30
+++ extern.h	21 Aug 2024 05:37:08 -0000
@@ -129,6 +129,7 @@ int	 forward(char *, FILE *, char *, int
 void	 free_child(pid_t);
 int	 from(void *);
 off_t	 fsize(FILE *);
+char*	 genmsgid(void);
 int	 getfold(char *, int);
 int	 gethfield(FILE *, char *, int, char **);
 int	 gethfromtty(struct header *, int);
Index: send.c
===================================================================
RCS file: /cvs/src/usr.bin/mail/send.c,v
diff -u -p -r1.26 send.c
--- send.c	8 Mar 2023 04:43:11 -0000	1.26
+++ send.c	21 Aug 2024 05:37:08 -0000
@@ -525,6 +525,8 @@ puthead(struct header *hp, FILE *fo, int
 		fmt("To:", hp->h_to, fo, w&GCOMMA), gotcha++;
 	if (hp->h_subject != NULL && w & GSUBJECT)
 		fprintf(fo, "Subject: %s\n", hp->h_subject), gotcha++;
+	if (fo != stdout)
+		fprintf(fo, "Message-ID: %s\n", genmsgid()), gotcha++;
 	if (hp->h_cc != NULL && w & GCC)
 		fmt("Cc:", hp->h_cc, fo, w&GCOMMA), gotcha++;
 	if (hp->h_bcc != NULL && w & GBCC)
Index: util.c
===================================================================
RCS file: /cvs/src/usr.bin/mail/util.c,v
diff -u -p -r1.2 util.c
--- util.c	26 Dec 2022 19:16:01 -0000	1.2
+++ util.c	21 Aug 2024 05:37:08 -0000
@@ -641,3 +641,29 @@ clearnew(void)
 		}
 	}
 }
+
+/* Generate Message-ID */
+char*
+genmsgid(void)
+{
+	time_t t = time(NULL);
+	struct tm tm = *localtime(&t);
+	static char date[] = "YYYYmmdd.HHMMSS";
+	static char hostname[HOST_NAME_MAX+1];
+	static char buf[sizeof(date) + sizeof(hostname) + 4];
+	size_t size = 0;
+	int error = 0;
+
+	if (gethostname(hostname, sizeof(hostname)))
+		errx(1, "genmsgid: gethostname");
+
+	if (strftime(date, sizeof(date), "%Y%m%d.%H%M%S", &tm)
+	    != sizeof(date) - 1)
+		errx(1, "genmsgid: strftime");
+
+	error = snprintf(buf, sizeof(buf), "<%s@%s>", date, hostname);
+	if (error >= sizeof(buf) || error < 0)
+		errx(1, "genmsgid: snprintf");
+
+	return(buf);
+}


-- 
Walter