Description of problem: "dnf install dovecot" took almost an hour to finish because it was generating the dhparams at %post. You must use a dovecot-init.service to generate the certificates, dh params, and other first-run setup. https://fedoraproject.org/wiki/Packaging:Initial_Service_Setup A similar case was discussed recently in the packaging mailing list: https://lists.fedoraproject.org/pipermail/packaging/2015-September/011008.html Version-Release number of selected component (if applicable): dovecot-2.2.18-4.fc23.armv7hl
It will propagate to other active Fedora releases later together with next dovecot update.