Adding Microsoft internal CA as a trusted signer.

Kevin.

Thanks for your reply.

I was made to believe that I had to establish the server side trust by the consultants who have been employed to implement Lync for us - but I've since found out that I don't really need to do so.

The external certs are working fine, and once I worked my way through the F5 Lync template (and, more importantly, the documentation provided by consultants, which was much more muddled!), I now find that the reverse proxy is working for Lync.

I was panicing because cURL was complaining about not being able to establish the veracity of the server certificate - but it seems I was freaking out over nothing.

Thanks again for confirming that I was just being stupid and worrying about nothing.