Until recently (perhaps a couple months) we have been successfully receiving silent posts to our webapp following transactions at authorize.net.
Now, our web logs are indicating that we are not receicing any silent posts from authorize.net. Our HTTPS URL is configured in the control panel. When I change our HTTPS to use HTTP, the post does appear in or web server log.
When I copy and paste the desired silent post URL to a browser, however, our http server does show receipt of the hit.
I've confirmed that our HTTPS cert is a commercial (i.e. not a self signed) cert and I have used a 3rd party site to verify the security settings of our site.
I've also confirmed with our ISP that it is not filtering out POSTs from blank user agents.
Any ideas what else we might check?