From the comments section on my previous link -
"Solved! You have to create two entries in the Manage Passwords. One of them is *.FQDN (the FQDN you use in the RPC over HTTPS proxy setting) and the other is the full DNS name of your mail server: *.yourdomain.com
Both entries should contain your user name in DOMAIN\username format and your password.
This worked for me."
This seemed to have worked for some. Make sure you also enable "Only connect to proxy servers that have the principal name..." options above and enter "msstd:mail.pm.telstra.com" in the box.