In the ~ directory of the root user on my debian wheezy server regularly appears file named dead.letter with (currently) the following content:orion : Jul 25 10:17:31 : root : unable to resolve host orionorion : Jul 26 02:17:18 : root : unable to resolve host orionorion : Jul 26 21:17:19 : root : unable to resolve host orionorion is the hostname of the server (and can normally be resolved since I have various services/programs using this hostname without problems). After some searching I figured that there is a cron job running hourly, i.e.17 * * * *  root    cd / && run-parts --report /etc/cron.hourlywhich could explain why those errors only appear 17 minutes after the full hour. The only script in /etc/cron.hourly is fake-hwclock with the following content:#!/bin/sh## Simple cron script - save the current clock periodically in case of# a power failure or other crashif (command -v fake-hwclock >/dev/null 2>&1) ; then      fake-hwclock savefiCan this produce those mysterious dead.letter? And why seems fake-hwclock save try to resolve the hostname?Edit: Some more information.Input of /etc/hosts:127.0.0.1       localhost::1             localhost ip6-localhost ip6-loopbackfe00::0         ip6-localnetff00::0         ip6-mcastprefixff02::1         ip6-allnodesff02::2         ip6-allrouters
Mysterious unable to resolve host in dead.letter
debian;cron;clock
Change the following line in /etc/hosts127.0.0.1       localhostto127.0.0.1       localhost  orionYour MTA was unable to resolve the domain name of your machine.