Never mind. It works now.
I went to the jre/bin folder and started the javacpl.exe. This gave
me a user interface where I could manage the Java certificates.
I then imported the CA root certificate and intermediate
certificate. After enabling TLS in the SDP outgoing mail server
settings, I was able to send TLS secured mail! I believe the issue was
with the intermediate certificate that was missing. To be sure I added
them both.
I have to keep in mind that when I do an upgrade, I check to see if the root certs are there and if not, add them again.
Iwan