I have a client whose site grinds to a halt every time they send out a mailing because of incoming traffic. We're using Varnish without SSL endpoint termination, so right now, we're not caching those pages at all.
However, even if we install SSL endpoint termination (or use HTTP links), the click-through links are unique, even though they return identical content. Is that content cacheable by Varnish? Or does using unique click-through links completely break caching?