OpenDKIM issues with new install

hi guys,

been building a new Virtualmin server running on Centos 7 and am getting the following error in the maillog… if I change localhost in both /etc/postfix/main.cf and /etc/opendkim.conf to 127.0.0.1 all works fine but the Virtualmin panel doesn’t detect DKIM as being enabled, only when I change it back to localhost does it start working

postfix/cleanup[6749]: fatal: host/service localhost/8891 not found: Name or service not known Feb 25 21:01:09 postfix/pickup[3473]: warning: maildrop/7578B416B70C: error writing 8627320CA49D: queue file write error

does anyone know how to make this work correctly?
localhost resolves without issue

Name: localhost
Address: 127.0.0.1

and /etc/hosts
127.0.0.1 servername.fqdn localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

also tried removing localhost from the ipv6 ::1 but that didn’t help.

and opendkim running without issue
● opendkim.service - DomainKeys Identified Mail (DKIM) Milter
Loaded: loaded (/usr/lib/systemd/system/opendkim.service; enabled; vendor preset: disabled)
Active: active (running) since Thu 2016-02-25 20:42:30 NZDT; 32min ago