http://openwebmail.org/openwebmail/doc/faq.txt
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INSTALLATION & STARTUP PROBLEMS
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Q: I got "SCRIPT_DIR not set in /etc/openwebmail_path.conf !" error?
A: On systems not passing perl script name as $0, openwebmail relies
on /etc/openwebmail_path.conf to know the directory it locates.
Please put 'the path of your openwebmail cgi directory' in the first
line of file /etc/openwebmail_path.conf.
For example, if the script is located at
/usr/local/apache/share/cgi-bin/openwebmail/openwebmail.pl,
then the content of /etc/openwebmail_path.conf should be:
/usr/local/apache/share/cgi-bin/openwebmail