Today we are announcing the availability of the 2023 H1 Cumulative Update (CU) for Exchange Server 2019 (aka CU13). CU13 includes fixes for customer reported issues along with all previously released...
Updated May 09, 2023
Version 3.0
Blog Post
LukasSMSFT
Microsoft
MicrosoftCVO123 IIS rewrite rule mitigations that were applied on a per-site/vDir level (stored in web.config files) are not retained. Server level mitigations (stored in applicationHost.config) will not be overwritten.
However, if an IIS rewrite rule mitigation has been overwritten during a CU installation, it'll be automatically reapplied by the Exchange Mitigation (EM) Service as long as the mitigation is still required/valid for the newly installed CU.
We've clarified this in the documentation: https://learn.microsoft.com/en-us/exchange/plan-and-deploy/custom-configuration-preservation?view=exchserver-2019#list-of-preserved-config-files-along-with-sections-and-keys-preserved