Good to hear.
I'll revise my earlier post for others that have related issue. I incorrectly thought that TorBirdy could be reconfigured to allow non-SSL/TLS-encrypted connections. Such an option could be useful when connecting to onion servers which always create end-to-end encrypted connections regardless. (end-to-end meaning icedove to onion server, not necessarily mail server).
But looking at the option again:
It specifically mentions "secure renegotiation", which is most likely referring to "Transport Layer Security (TLS) Renegotiation Indication Extension". And not SSL/TLS in general. It would probably be considered too dangerous to include an option that would send mail in-the-clear to non-onion servers. I've never come across an email provider that didn't offer TLS, so unable to test. Perhaps Hillary offered a non-TLS onion on her server?