You can configure EXM.RendererUrl
in the Sitecore.EmailExperience.Core.config
config file.
In case the setting is empty, the RendererUrl
is resolved on the first request to the application. In the <httpRequestBegin>
pipeline, there is a Sitecore.Modules.EmailCampaign.Core.Pipelines.HttpRequestBegin.OnHttpRequestBegin
processor that that does that:
GlobalSettings.RendererUrl = WebUtil.GetServerUrl(args.HttpContext.Request.Url, false);
You said that it worked ok previously on HTTP, but after you switched to HTTPS, it does not work. First I would focus on fixing the SSL/TLS issue. I bet that there is some problem with the certificate.