mailgraph.cgi is not copied/linked to /var/www/localhost/cgi-bin/ so you need to copy it from /usr/share/webapps/mailgraph/1.13/hostroot/cgi-bin. I don't know how this is normally handled, but it doesn't seem right to me.
Works fine for me. Use webapp-config after emerging, as mentioned in the post-install info.
> Use webapp-config after emerging, as mentioned in the > post-install info. Where ? All that I can see after installing is there : * * Mailgraph will run as user mgraph with group adm by default. * This can be changed in /etc/conf.d/mailgraph if it doesn't fit. * Remember to adjust MG_DAEMON_LOG, MG_DAEMON_PID and MG_DAEMON_RRD * as well! * * * Please make sure the MG_LOGFILE (default: /var/log/messages) is readable * by group adm or change MG_DAEMON_GID in /etc/conf.d/mailgraph accordingly! * * Please make sure *all* mail related logs (MTA, spamfilter, virus scanner) * go to the file /var/log/messages or change MG_LOGFILE in * /etc/conf.d/mailgraph accordingly! Otherwise mailgraph won't get to know * the corresponding events (virus/spam mail found etc.). * * * Checking for user apache * * Adding user apache to group mgraph so the included * CGI script is able to read the mailgraph RRD files