Bind to INADDR_ANY for DNS lookups rather than the interface address.

This allows using a private DNS server when an external interface is specified
(ie: DNS Server of 127.0.0.1 with an interface address specified)

src/sbbs3/mailsrvr.c

@@ -3839,7 +3839,7 @@ static void sendmail_thread(void* arg)
 							continue;
 						}
 						lprintf(LOG_DEBUG,"0000 SEND getting MX records for %s from %s",p,dns_server);
-						if((i=dns_getmx(p, mx, mx2, startup->interface_addr, dns
+						if((i=dns_getmx(p, mx, mx2, INADDR_ANY, dns
 							,startup->options&MAIL_OPT_USE_TCP_DNS ? TRUE : FALSE
 							,TIMEOUT_THREAD_WAIT/2))!=0) {
 							remove_msg_intransit(&smb,&msg);