We are aware of an issue impacting all Zimbra email services. Our technical operations teams are currently investigating the issue and updates will be provided as they come to hand.
Please note the following contact methods:
SOC - https://secure-iss-soc.au.4me.com/
Technical Operations/ AppServe: https://secure-iss-appserve.au.4me.com/
or contact us via phone on +61 7 5528 2373