[Sysinfo] Warning: could not send message for past 4 hours

[Mail Delivery Subsystem]

    **********************************************
    **      THIS IS A WARNING MESSAGE ONLY      **
    **  YOU DO NOT NEED TO RESEND YOUR MESSAGE  **
    **********************************************

The original message was received at Tue, 9 Jul 2013 01:02:08 -0400
from localhost.localdomain [127.0.0.1]

   ----- Transcript of session follows -----
sysinfo at int.autonlab.org... Deferred: mail.int.autonlab.org.: No route to host
Warning: message still undelivered after 4 hours
Will keep trying until message is 5 days old
-------------- next part --------------
An embedded message was scrubbed...
From: root at lofty.int.autonlab.org (Cron Daemon)
Subject: Cron <root at lofty> /root/bin/backup_thishost.sh
Date: Tue, 9 Jul 2013 01:00:01 -0400
Size: 1233
URL: <https://mailman.srv.cs.cmu.edu/mailman/private/autonlab-sysinfo/attachments/20130709/e2ca8b22/attachment.mht>