It seems I can't view attachments nor the Original of any messages. Tomcat gives me a 404:
I've set up Zimbra to use port 5050 (http) and 6060 (https), so not to interfere with Apache, or future default installations of Tomcat or JBoss. I did test the setup on my local machine with such configs, prior to set it up on the remote, with success.
HTTP Status 404 - no such item
type Status report
message no such item
description The requested resource (no such item) is not available.