Add the MAILNAME and MAILNAMEFILE config options.

--- a/conf.c
+++ b/conf.c
@@ -240,6 +240,14 @@
 				if (data != NULL)
 					config->dbounceprog = strdup(data);
 			}
+			else if (strcmp(word, "MAILNAME") == 0) {
+				if (data != NULL)
+					config->mailname = strdup(data);
+			}
+			else if (strcmp(word, "MAILNAMEFILE") == 0) {
+				if (data != NULL)
+					config->mailnamefile = strdup(data);
+			}
 			else if (strcmp(word, "VIRTUAL") == 0)
 				config->features |= VIRTUAL;
 			else if (strcmp(word, "STARTTLS") == 0)
--- a/dma.8
+++ b/dma.8
@@ -242,6 +242,20 @@
 .Xc
 Uncomment if you want the bounce message to include the complete original
 message, not just the headers.
+.It Ic MAILNAME Xo
+(string, default=empty)
+.Xc
+The name to be used when introducing this host, if different from
+the result of
+.Xr hostname 1 .
+If specified, this option overrides
+.Sq MAILNAMEFILE .
+.It Ic MAILNAMEFILE Xo
+(string, default=empty)
+.Xc
+The name of the file to read the
+.Sq MAILNAME
+from.
 .El
 .Ss virtusertable
 The
--- a/dma.c
+++ b/dma.c
@@ -81,10 +81,38 @@
 hostname(void)
 {
 	static char name[MAXHOSTNAMELEN+1];
+	int initialized = 0;
+	FILE *fp;
+	size_t len;
+
+	if (initialized)
+		return (name);
 
+	if (config->mailname != NULL && config->mailname[0] != '\0') {
+		snprintf(name, sizeof(name), "%s", config->mailname);
+		initialized = 1;
+		return (name);
+	}
+	if (config->mailnamefile != NULL && config->mailnamefile[0] != '\0') {
+		fp = fopen(config->mailnamefile, "r");
+		if (fp != NULL) {
+			if (fgets(name, sizeof(name), fp) != NULL) {
+				len = strlen(name);
+				while (len > 0 &&
+				    (name[len - 1] == '\r' ||
+				     name[len - 1] == '\n'))
+					name[--len] = '\0';
+				if (name[0] != '\0') {
+					initialized = 1;
+					return (name);
+				}
+			}
+			fclose(fp);
+		}
+	}
 	if (gethostname(name, sizeof(name)) != 0)
 		strcpy(name, "(unknown hostname)");
-
+	initialized = 1;
 	return name;
 }
 
--- a/dma.h
+++ b/dma.h
@@ -122,6 +122,8 @@
 	SSL *ssl;
 #endif /* HAVE_CRYPTO */
 	char *dbounceprog;
+	char *mailname;
+	char *mailnamefile;
 };
 
 
--- a/etc/dma.conf
+++ b/etc/dma.conf
@@ -49,3 +49,11 @@
 # Uncomment if you want the bounce message to include the complete original
 # message, not just the headers.
 #FULLBOUNCE
+
+# The name to be used when introducing this host, if different from
+# the result of "hostname".  If specified, this overrides MAILNAMEFILE.
+#MAILNAME mail.example.net
+
+# The name of the file to read the MAILNAME from; if this file is not
+# present, the result of "hostname" will be used.
+#MAILNAMEFILE /etc/mailname