creating and logging a daily cron job

[michael <cs@networkingnewsletter.org.uk>]

If I wish to have, say, a backup script running daily by the system (ie
with su privileges) and to have access to any std out/err output what's
the recommended Debian way to do so?

I've tried
a) create $HOME/bin/backup.sh script
b) sudo ln -is $HOME/bin/backup.sh /etc/cron.daily

and it appears to run each day. However, I can't find where std out/err
is going to - there's nothing in /var/log/syslog for example.

Note I don't want to receive mail for all cron jobs run by the system so
I presume setting MAILTO in /etc/crontab is not the way forward.

Many thanks, M