If a cron job has output, and only if it has output, this output is mailed to the cron job owner. So, look for the user's e-mail. The system e-mails are stored at /var/spool/mail.
Cron does not use a mail program like thunderbird or evolution, if it is what you mean. It uses whatever is listening on SMTP port (25/TCP) on localhost. Theses programs are called MTA (Mail Transport Agent) and commom MTAs are sendmail or postfix.
You can configure a program like evolution to read e-mails on a local system. Specify a file at /var/spool/mail as source.
You can use a program like "mail" in command line to read e-mails in text mode, but I don't advice you to do this if you is a newbie.
Code:
[root@agente86 nagios]# ls -l /var/spool/mail
total 1888
...
-rw-rw---- 1 nagios mail 1758440 2007-06-13 09:46 nagios
...
[root@agente86 nagios]# mail -f /var/spool/mail/nagios
Mail version 8.1 6/6/93. Type ? for help.
"/var/spool/mail/nagios": 697 messages 697 new
>N 1 MAILER-DAEMON@agente Mon Jun 11 17:28 67/2592 "Warning: could not send message for past 4 hours"
N 2 MAILER-DAEMON@agente Mon Jun 11 17:28 67/2597 "Warning: could not send message for past 4 hours"
N 3 MAILER-DAEMON@agente Mon Jun 11 17:28 67/2599 "Warning: could not send message for past 4 hours"
...
& x
[root@agente86 nagios]#
