Although sendmail package is the 'default' package of 'base' group, it's also possible that no package that provides MTA is installed.
redhat-lsb-4.1-5.fc17 has been submitted as an update for Fedora 17. https://admin.fedoraproject.org/updates/redhat-lsb-4.1-5.fc17
Package redhat-lsb-4.1-5.fc17: * should fix your issue, * was pushed to the Fedora 17 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing redhat-lsb-4.1-5.fc17' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2012-10194/redhat-lsb-4.1-5.fc17 then log in and leave karma (feedback).
redhat-lsb-4.1-5.fc17 has been pushed to the Fedora 17 stable repository. If problems still persist, please make note of it in this bug report.