The spec file that comes with the tar.gz. or tar.bz2. files of Sylpheed 2.7.0 seems to be broken. When trying to build an RPM from either of these files, I did get an RPM build error complaining about unpackaged files. Adding the lines
%{_includedir}/%{name}/*.*
%{_includedir}/%{name}/*/*
%{_libdir}/*.*
at the end of the spec file helped.
Regards
F. Fabian