Where can I find relevant logs to solve a problem?

According to the affected service look at these logs.

For general problems look at

• /var/log/apache2/error.log
• /var/log/apache2/suexec.log

If a specific domain is affected, also look at:

• /var/log/apache2/users/affected.domain-error.log

• /var/log/mail.log (this one contains all information)
• /var/log/mail.err (this one contains only errors)

• grep named /var/log/syslog

• /var/log/ispcp/ispcp-*

To get detailed logs here you have to activate debugging in /etc/ispcp/ispcp.conf.