OS related topics
From OpenCms Wiki
Email problem on OpenCMS 7.0.4 installed on CentOS5.3/Tomcat 5.5.27
you cannot send out email after default installation (I'll post the error message later). All you need to do is to delete /var/lib/tomcat5/webapps/ROOT/WEB-INF/lib/mail.jar (assuming you install opencms as ROOT to eliminate the /opencms/opencms). Then OpenCMS will use the $tomcat5$/common/lib/[javamail].jar to send out email. Email works then.
Of course, you need to have sendmail installed on CentOS.
Vista
If you are getting exceptions related to database when installing OpenCMS on MS Vista, try disabling the windows firewall or adding specific exceptions for opencms and related apps such as the database.