This browser is no longer supported.
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(144, 3%, 23%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EN%3C/text%3E%3C/svg%3E)
Hi Everyone,
We have some Mail Flow Rules configured on our Local Exchange 2016 Server. Will CU 20 override these customizations? Please advise.
Logbi
No, absolutely not. Upgrading will not affect any transport rule.
Those are stored in AD, not in the server config.
Awesome! I read this article regarding latest CU update and it says customized IIS and Exchange Server configuration will be overwritten though the list of config files were not specified. Do you guys happen to know those configuration files being mentioned and their locations?
Thank you so much!
Logbi
that refers to files such as:
https://learn.microsoft.com/en-us/exchange/clients/outlook-on-the-web/customize-outlook-on-the-web?view=exchserver-2019
and
%ExchangeInstallPath%Bin\EdgeTransport.exe.config
Honestly, most people do not change any of those settings. I would upgrade and not worry about it. :)
Note that not all customizations get overwritten either. The transport one will not get overwritten.
Its typically just an custom IIS setting and even if that is overwritten, its easy to fix and does not affect functionality.
Hi AndyDavid,
Thank you so much for your help! Hearing these from an expert really boost my confidence in pushing this CU to our Exchange Server 2016. :)
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(25.6, 67%, 12%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EJS%3C/text%3E%3C/svg%3E)
Hi @Noctis0791
Agree with the reply above from Andy, mailflow rules will not be override after updating CU.
And if you have customised the files list above, it's better to backup and reconfigure them after the update.
Below threads discussed the similar issue for your reference:
IIS, Default website, Exchange and our company website
Exchange Server 2016 CU11 install
Installing exchange CU precautions and effects on custom configuration
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
Thanks as well joyceshen-MSFT.