smtp.cyberonic.com stopped forwarding outbound messages as of last Thursday. It receives messages just fine, and will deliver locally, but doesn't forward them on to other MTA's. I spoke with Cyberonic support and the woman I spoke with didn't know that smpt.cyberonic.com existed - she asked me to switch my outbound gateway to mail.cyberonic.com, the implication being they use mail.cyberonic.com for both inbound and outbound now. I asked her to open a trouble ticket on smtp.cyberonic.com but nothing appears to have been done yet - I have an unknown amount of outbound email stuck in smtp.cyberonic.com, thought I am back up and running using mail.cyberonic.com as my outbound gateway.
In a possibly related matter, inbound mail delivery from mail.cyberonic.com was down most of the weekend - just came back this morning.