Everyone got kicked out of Outlook this morning at 8:40

Exchange had a few System errors:

A process serving application pool 'MSExchangeMapiFrontEndAppPool' suffered a fatal communication error with the Windows Process Activation Service. The process id was '7812'. The data field contains the error number.

The Microsoft Exchange Transport service terminated unexpectedly.  It has done this 1 time(s).  The following corrective action will be taken in 5000 milliseconds: Restart the service.

We are non SP1 on CU3,  I'm looking to upgrade to CU8 soon... are there any other possible causes here?  

Is there an upgrade path from CU3 to CU8 that I need to take?

• Edited by JoeFri 18 hours 1 minutes ago

First thing you need to do is to upgrade to CU8 and see if the issue reoccurs.  If the issue reoccurs than it might be good to engage MSFT support to see why the transport service is crashing.  I would say to engage them now, but CU3 is way older than the officially supported 2 most current CUs. 

P.S. You can go directly from CU3 to CU8.  

Thanks Hinte, I'm going to upgrade to CU8 in my dev environment and test.  and schedule some time to upgrade to CU8.

DO you have the contact info for MSFT if they issue continues?

Use this:

https://support.microsoft.com/en-us?wa=wsignin1.0