Please drop the NetworkManager-glib-devel BR. The package is going away soon. You can find a patch here: http://www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=3938
This bug appears to have been reported against 'rawhide' during the Fedora 28 development cycle. Changing version to '28'.
The patch misses a second NM_CHECK_VERSION that needs to be removed, too, or else the code would fail. https://src.fedoraproject.org/rpms/claws-mail/blob/master/f/claws-mail-3.16.0-libnm.patch
Built for F28. F29 not yet because docbook-utils-0.6.14-45.fc29 is still pending.