Microsoft has released security updates for vulnerabilities found in:
Exchange Server 2013
Exchange Server 2016
Exchange Server 2019
These updates are available for the following specific...
Updated May 04, 2021
Version 8.0
Blog Post
First 3 steps to install april security update:
1. Put the server in maintenance mode.
2. Reboot the server.
3. Install security update
Is it required to reboot the server after placing the server in maintenance mode? And if so, why is it required to first reboot?
https://docs.microsoft.com/en-us/exchange/high-availability/manage-ha/manage-dags?view=exchserver-2019#performing-maintenance-on-dag-members states:
Installing updates on DAG members
1. Use the steps described above to put the DAG member in maintenance mode.
2. Install the update.
3. Use the steps described above to take the DAG member out of maintenance mode and put it back into production.
4. Optionally, use the RedistributeActiveDatabases.ps1 script to rebalance the active database copies across the DAG.