Exchange 2016 - High CPU utilization by Microsoft Exchange Replication Service (MSExchangeMailboxReplication)

I had faced with that issue on my work and with Microsoft support we found the core issue and solved it.

Unfortunately, I haven't been able to reproduce this issue in my home lab, but I'll try to describe all main points.

Procmon was showing that "MSExchangeMailboxReplication.exe" process always (hundreds of times per second) try to open (RegOpenKey) "HKLM\SOFTWARE\Microsoft\ExchangeServer\v15\ActiveManager\TestOverride" reg key.

Adding the "TestOverride" registry key doesn't solve the problem. The process started to searching other keys.

Exchange 2016 - Issues with ECP/OWA after installing updates/KB

For several reasons after installation updates/KB (for example KB4536987) you may faced with some backfires. I collected 3 type of issues and their fixes.

Issue #1 - Lack os styles on ECP page

After authentication on ECP page you may see only text and hyperlinks without any images and styles.

How to fix

Run the script "C:\Program Files\Microsoft\Exchange Server\V15\Bin\UpdateCas.ps1" or do following manual steps:

• Go to "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\ecp" folder and find the folder with latest version number of your server (e.g. "15.1.1913.7") and it will be empty.
• Open folder with previous version number (e.g. "15.1.1913.5") and copy all data to the new folder (e.g. "15.1.1913.7").
• Restart IIS. Reload the ECP page.