dead letter recieved from cron

[Tapas Mishra]

I was taking backup of my server when I noticed a file named dead.letter
what is that it is in root folder and its contents I have not created.

Here are the contents

To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Thu Sep 23 04:00:01 IST 2010
CRON-APT SLEEP: 274, Thu Sep 23 04:04:35 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.
To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Fri Sep 24 04:00:01 IST 2010
CRON-APT SLEEP: 313, Fri Sep 24 04:05:14 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.
To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Sat Sep 25 04:00:01 IST 2010
CRON-APT SLEEP: 1383, Sat Sep 25 04:23:04 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.
To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Sun Sep 26 04:00:01 IST 2010
CRON-APT SLEEP: 2118, Sun Sep 26 04:35:19 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.
To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Mon Sep 27 04:00:01 IST 2010
CRON-APT SLEEP: 514, Mon Sep 27 04:08:35 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.
To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Tue Sep 28 04:00:01 IST 2010
CRON-APT SLEEP: 2393, Tue Sep 28 04:39:54 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.
To: root
Subject: CRON-APT completed on server [/etc/cron-apt/config]

CRON-APT RUN [/etc/cron-apt/config]: Wed Sep 29 04:00:01 IST 2010
CRON-APT SLEEP: 3209, Wed Sep 29 04:53:30 IST 2010
CRON-APT ACTION: 0-update
CRON-APT LINE: /usr/bin/apt-get update -o quiet=2
W: Failed to fetch
http://debian.adenu.ia.uned.es/apt/dists/lucid/main/binary-amd64/Packages.gz
 404  Not Found

E: Some index files failed to download, they have been ignored, or old
ones used instead.

-- 
Tapas