Exchange send connector TLS stopped working after heartbleed.

I have an issue with an Exchange 2007 install, that was working just fine until heartbleed news came out.  Suddenly the "smarthost" stopped working, and outbound emails weren't going out.

For some reason, pointing the exchange server at a different smarthost with TLS enabled worked, or disabling TLS on the existing smarthost made it work fine.

This server is using "Dyn Standard SMTP" as it's smarthost. 

I'm wondering if somehow Exchange doesn't like the new TLS certificate? Because Dyn probably got new certificates when heart-bleed happened.