Terminate each local message by an empty line

According to RFC 4155, each message in the mbox database must be
terminated by an empty line, containing a single end-of-line marker.
That doesn't match the current behavior, where dma writes this EOL
marker at the same time with the following separator line on each
subsequent local delivery, which effectively changes the previous
message, and may leave the new one in a non-conformant state.

Author: Alexey Sukhoguzov

local.c

@@ -130,7 +130,6 @@ deliver_local(struct qitem *it)
 	char fn[PATH_MAX+1];
 	char line[1000];
 	const char *sender;
-	const char *newline = "\n";
 	size_t linelen;
 	int tries = 0;
 	int mbox;
@@ -184,10 +183,6 @@ deliver_local(struct qitem *it)
 
 	mboxlen = lseek(mbox, 0, SEEK_END);
 
-	/* New mails start with \nFrom ...., unless we're at the beginning of the mbox */
-	if (mboxlen == 0)
-		newline = "";
-
 	/* If we're bouncing a message, claim it comes from MAILER-DAEMON */
 	sender = it->sender;
 	if (strcmp(sender, "") == 0)
@@ -198,7 +193,7 @@ deliver_local(struct qitem *it)
 		goto out;
 	}
 
-	error = snprintf(line, sizeof(line), "%sFrom %s %s", newline, sender, ctime(&now));
+	error = snprintf(line, sizeof(line), "From %s %s", sender, ctime(&now));
 	if (error < 0 || (size_t)error >= sizeof(line)) {
 		syslog(LOG_NOTICE, "local delivery deferred: can not write header: %m");
 		goto out;
@@ -241,6 +236,11 @@ deliver_local(struct qitem *it)
 		if ((size_t)write(mbox, line, linelen) != linelen)
 			goto wrerror;
 	}
+
+	/* Each message in the mbox must be terminated by an empty line. */
+	if (write(mbox, "\n", 1) != 1)
+		goto wrerror;
+
 	close(mbox);
 	return (0);