TMG - 0x80090325 -Certificate Chain was issued by an authority that is not trusted

Question

Hello,
I am having some problems with testing a OWA (SSL) rule. I get that message.
The TMG belongs to the domain and therefore as far as I know it gets the root certificate of my CA (I have deployed a Enterprise CA for my domain).
That is why I don't understand the message: "...that is not trusted."
The exact message:
Testing https://mail.mydomain.eu/owa
Category: Destination server certificate error
Error details: 0x80090325 - The certificate chain was issued by an authority that is not trusted
Thanks in advance!
Luis Olías Técnico/Admon Sistemas . Sevilla (España - Spain)

Answer 1

Thanks Keith for your reply and apologies for the delay in my answer.
I coud not wait and I reinstalled the whole machine (W28k R2 + TMG 2010) . I suppose I am still a bad troubleshooter, I have experience setting up ISA, TMG, PKI, Active directory but to a certain extent.
1. Yes, I saw it when hitting the button "Test Rule" in the Publising rule in the TMG machine.
2. No, it did not work in this implementation but it has worked in others, this is not difficult to set up, until now, hehe.
3. You said: "...If you are seeing it when running "Test Rule" then it simply means that TMG does not trust something about the certificate that is on your Exchange Server...."
But the certificates are auto-enrolled, and when I saw the details of the certificates they all are "valid" , there is a "valid" message.
4. You wrote: "...Easiest way see everything is create an access rule that allows traffic from the LocalHost of TMG to the CAS and open up a web browser. Does the web browser complain?..."
But as I said, I re-installed the whole thing because nobody jumped in here , and I needed to move forward, I hope you understand.
5. S Guna kindly proposed this:
If you are using internal CA,
You need to import the Root CA certificate to TMG servers.
Import Private Key of the certificate to Server personal
Create a Exchange publishing Rule and Point the lisitner to the Correct certificate.
Since you are using internal CA, You need to import the Root CA certificate to all the client browers from where you are accessing OWA
But I think I do not have to perform any of those tasks, although I am not an expert but have worked with Certificate for one year or so.
Luis Olías Técnico/Admon Sistemas . Sevilla (España - Spain)