Have had Exchange 2013 running on a Virtual machine for a couple of months now without issues other than some serious throttling issues we bypassed exchange and resolved.

I installed a second Exchange 2013 server on a physical server and Created an active passive DAG on Sunday the 18th.  Everything tested as far as email flowing inbound and outbound, both plain text and through our ZIX server.

On Thursday the 23rd, everyone in the company received a certificate warning when logging into outlook any versin.

At the same time, noticed that any job from any of our 4 job servers that had email tasks going through the exchange server also failed with the following error.

Source: Send Duplicate Attempt Send Mail Task     Description: An error occurred with the following error message: "Service not available, closing transmission channel. The server response was: 4.3.2 Service not available".

We drained the Physical Exchange server queues and powered it down, no more certificate errors, and no more jobs failing.

Not sure where to begin looking.

• Edited by timwtaylor 15 hours 14 minutes ago

Are these multi-role servers? Sounds as if the CAs role on the new server didn't have a valid certificate.

Also, what do you consider an a Active/passive DAG?