To get Autodiscover working on a certificate that does not have any extra SAN’s available apart from it’s main Conical Name on the Certificate , you will need to use either a autodiscoer.xml file hosted on the companies main website or create a SRV record with the registrar.
The registrar was Melbourne IT , who for some reason don’t have valid DNS validation so records get stuck “Publishing”. After trial and error I finally got the records needed and beat their own Helpdesk by 2 Weeks to the fix.
Name : companydomain.com. ( remember dot on the end )
TTL : Can be left @ their default 86400 but should be 3600
Priority : 0
Port : 443
Weight : 0
Service : _autodiscover
Protocol : _tcp
Target : mail.domain.com ( domain name on the CN Cert) ( remember dot on the end )