This is a "known to Microsoft" issue that only affects some users. To correct the error, make the following changes to your domain's DNS zone records.
"HOW TO" STEPS
Close Outlook.
Delete the autodiscover CNAME from your domain's DNS zone.
Adding an SRV record that contains the following information:
Service: _autodiscover
Protocol: _tcp
Name: @
Priority: 0
Weight: 0
Port: 443
Target: autodiscover.ezyexchange.net.au.
Depending on your DNS control panel, the structure of the SRV record may vary slightly. For example, in cPanel, it will look like this ...
_autodiscover._tcp IN SRV 0 0 443 autodiscover.ezyexchange.net.au.
In other control panels, they may ask for a record name. Give it "@" (without quotes). This will be interpreted as your domain name.
Also, be sure to remember the trailing dot in autodiscover.ezyexchange.net.au.
Once this DNS changes has propagated, you should find that the Autodiscover certificate errors will cease.
