Taking away DKIM signing deletes the DKIM data from LDAP, and new email messages are now not signed for your domain. The Kerberos token sent through the Authorization HTTP header coupled with jetty’s keytab file can detect/authenticate the consumer. However the Zimbra proxy (nginx based mostly) logs including /decide/zimbra/log/nginx.obtain.log https://www.hostscheap.com/zimbra-support-premium-service