Explanations
The Event Id 8010 implies that it is not possible to deliver at least 1 journal message to the journal report mailbox.
When any journal message is rejected by means of any reason, the transport process intercepts the NDR (Non Delivery Report) procedure & tries itself to transfer messages in retry mode.
Note: If the users do not solve this error, it might be the possibility that the messages will build in queues.
Resolutions
For solving this error, users first need to determine the reason why the journal message is rejected. Thereafter, go for fixing that error. So, to find the error, go through these steps:
In case, if you are not familiar with doing all the above operations, you can take the help of Exchange Tools that Microsoft offers. This tool helps the users as well as administrators in analyzing & troubleshooting the Exchange related issues.