this is almost certainly an SAN ( subject alternative name ) issue. Make sure that you have SAN`s for all possible references to the server in your cert. For instance mail.yourdomain.com for external the servername.FQDN.com for internal referencing.
Additional you will need autodiscover.fqdn
As the post above mentions you will need to run the ps1 script for setting the autodiscover service url.
Hi Jobos,
I saw this , which is scarily my website so registered so I could help, if you are relaying externally then try adding anonymous aswell as exchanger servers to the connector
thanks
Allen