SELinux is preventing amavisd from using the dac_override capability.                                                                                                                                                               
*****  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 amavisd 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 'amavisd' --raw | audit2allow -M my-amavisd
# semodule -X 300 -i my-amavisd.pp


Additional Information:
Source Context                system_u:system_r:antivirus_t:s0
Target Context                system_u:system_r:antivirus_t:s0
Target Objects                Unknown [ capability ]
Source                        amavisd
Source Path                   amavisd
Port                          <Unknown>
Host                          helio
Source RPM Packages
Target RPM Packages
Policy RPM                    selinux-policy-3.14.1-21.fc28.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     helio
Platform                      Linux helio 4.16.2-300.fc28.x86_64 #1 SMP Thu Apr
                              12 14:58:07 UTC 2018 x86_64 x86_64
Alert Count                   15
First Seen                    2018-04-17 16:08:25 CEST
Last Seen                     2018-04-17 18:13:48 CEST
Local ID                      8f04bc4b-331a-4dd6-840b-9ad69aee5269

Raw Audit Messages
type=AVC msg=audit(1523981628.373:570): avc:  denied  { dac_override } for  pid=3667 comm="amavisd" capability=1  scontext=system_u:system_r:antivirus_t:s0 tcontext=system_u:system_r:antivirus_t:s0 tclass=capability permissive=0


Hash: amavisd,antivirus_t,antivirus_t,capability,dac_override