Do you see anything across your logging in and around the time you saw the spike? Usually something is going on and I'd bet you have a user doing a big sync job or something along those lines :-)

IN what log would that appear??

It is very hard to trace such activity but if you happen to experience it again, run the network monitor via performance monitor and check which IP pull the highest traffic and match again the IMAP log

Doesnt give away anything....

Same issue but all versions. We are running 8888 as well now. Today we had to restart due to this 100 cpu issue. Sometimes it recovers on its own. We've been dealing with this for a few years.

Crazy. I have only seen it once before on an older buld (85XX)

Unfortunately Brian I can't indicate a single log for this. The source of temporary CPU usage could come from a variety of places, but the most common source is sync, indexing, someone sending to a large mailing list, etc. 

To my understanding, jetBrains can dump a file with more information. However, it must be captured while the CPU spike is actively occurring. This is a challenge. 

Hello, We are planning to update from 8251 to 8888.

We need to ensure that such issues do not occur after the update.

Could you please share your environment details? 

How many users do you have, and do you use Outlook?

We have about 1800 users, and approximately 1000 of them use Outlook.

Cant guarantee anything. We use outlook on 100% of the clients along with IOS and Android.

We have no idea at all. Sometimes our team is forced to restart SmarterMail in the middle of the day. This issue never happens during the night. Many tickets have been submitted, but unresolved.

Happening to another solution gives us some hope the issue is found.