OK - I'm an idiot. I'll just admit that up front and get it out of the way.
Now that that's settled, what is the difference between "SSL" and "TLS" in a MUA - particularly Thunderbird - in a Postfix context? I would have sworn I used to use Thunderbird with "SSL" specified and connected to my Postfix servers fine. Now, I can only connect in "TLS" mode. What did I break? -- Daniel