Fedora 18 changes the way how to work with services in spec files. It introduces new macros - %systemd_post, %systemd_preun and %systemd_postun; which replace scriptlets from Fedora 17 and older (see https://fedoraproject.org/wiki/Packaging:ScriptletSnippets#Systemd, https://bugzilla.redhat.com/show_bug.cgi?id=850016).
Created attachment 632763 [details] Patch replaces scriptlets with new systemd macros You had service ... stop and systemctl stop call in preun part and those two commands do basically the same thing - stopping the service. So I replaced it with %systemd_preun macro which calls only systemctl stop. If the service call was there for any special purpose, let me know and I will correct the patch.
mailman-2.1.15-5.fc18 has been submitted as an update for Fedora 18. https://admin.fedoraproject.org/updates/mailman-2.1.15-5.fc18
Package mailman-2.1.15-5.fc18: * should fix your issue, * was pushed to the Fedora 18 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing mailman-2.1.15-5.fc18' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2012-17340/mailman-2.1.15-5.fc18 then log in and leave karma (feedback).
mailman-2.1.15-5.fc18 has been pushed to the Fedora 18 stable repository. If problems still persist, please make note of it in this bug report.