Hi @Иван Кордяк,
Welcome to the Microsoft Q&A platform!
Event ID 5011 typically indicates that the IIS application pool for Exchange has crashed. This can be caused by a variety of factors, including third-party software conflicts such as backup agents.
Based on your description, removing the CyberProtect backup agent seems to resolve the issue, which suggests they may be the culprit. This is consistent with other reports where third-party software, particularly backup or antivirus solutions, has caused similar issues.
Here are a few steps you can take to further investigate and potentially resolve the issue:
- Even though you mentioned that there is no issue with resource utilization, it is still worth monitoring CPU, memory, and disk usage at the time of the crash. Tools such as Performance Monitor or Process Explorer can help with this.
- Look for any related events in Event Viewer, especially at the time of the crash. Events 15004-15007 in the Application log may provide additional clues.
- As a temporary measure, you can try to recycle the affected application pool from IIS Manager. This can sometimes help stabilize the service.
- If the issue persists, make sure your Exchange Server OAuth certificate is not expired, as this can also cause the application pool to crash.
Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.
Best,
Jake Zhang