Although this is a premium feature that we have paid for it is clear after testing that DNN does not properly support SSL Offloading.  Our top navigation, SiteMap, Search Results, and popus such as page settings all use HTTP URLs even though we have everything configured correctly.

We have determined the root cause to be a bug in DNN, specifically it appears to be within Globals.AddHTTP() -- this method is used throughout the DNN source code and within the Friendly URL provider (which we are using). When using SSL offloading this method DOES NOT check for the SSL header but instead calls the ASP.Net HttpContext.Current.Request.IsSecureConnection property to make the sole determination if a http:// or https:// schema is added to the URL. ASP.Net's IsSecureConnection basically looks at the HTTPS server variable which is not going to be set when using SSL Offloading and as a result all absolute URLs are built as HTTP.

I have been struggling trying to get DNN support to reproduce/test and confirm my findings. Although this is a high priority issue for us, and have have requested this issue get escalated numerous times, our support engineer has refused to escalate nor give our support ticket the proper attention/priority. This has lead me to have to code-walk and test to find this bug myself. 

I would appreciate anyone in the community with more leverage than I (only a paying customer) to see if they can help me lean on DNN to do the right thing and help get this issue the attention it deserves. At this point I am really not sure what we are paying for when it comes to support from DNN. This is our first support case with DNN and have only been using the platform for about two months and so far I am regretting that decision.