SELinux is preventing spamd from using the 'dac_override' capabilities.

*****  Plugin dac_override (91.4 confidence) suggests   **********************

If you want to help identify if domain needs this access or you have a file with the wrong permissions on your system
Then turn on full auditing to get path information about the offending file and generate the error again.
Do

Turn on full auditing
# auditctl -w /etc/shadow -p w
Try to recreate AVC. Then execute
# ausearch -m avc -ts recent
If you see PATH record check ownership/permissions on file, and fix it,
otherwise report as a bugzilla.

*****  Plugin catchall (9.59 confidence) suggests   **************************

If you believe that spamd should have the dac_override capability by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# ausearch -c 'spamd' --raw | audit2allow -M my-spamd
# semodule -X 300 -i my-spamd.pp

Additional Information:
Source Context                system_u:system_r:spamd_t:s0
Target Context                system_u:system_r:spamd_t:s0
Target Objects                Unknown [ capability ]
Source                        spamd
Source Path                   spamd
Port                          <Unknown>
Host                          (removed)
Source RPM Packages           
Target RPM Packages           
Policy RPM                    selinux-policy-3.14.1-32.fc28.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     (removed)
Platform                      Linux (removed) 4.16.14-300.fc28.x86_64 #1 SMP Tue
                              Jun 5 16:23:44 UTC 2018 x86_64 x86_64
Alert Count                   4
First Seen                    2018-06-10 10:24:49 EDT
Last Seen                     2018-06-12 00:52:22 EDT
Local ID                      6910e659-ab84-4de8-8ec5-87fa51bf4015

Raw Audit Messages
type=AVC msg=audit(1528779142.714:5790): avc:  denied  { dac_override } for  pid=12914 comm="spamd" capability=1  scontext=system_u:system_r:spamd_t:s0 tcontext=system_u:system_r:spamd_t:s0 tclass=capability permissive=0


Hash: spamd,spamd_t,spamd_t,capability,dac_override