Does Exchange Server Cumulative Update auto-backup web.config files?

[John_Lee2025]

Hello all,

Exchange Server Cumulative Update newbie here.

I take heed of the following advice from https://learn.microsoft.com/en-us/exchange/plan-and-deploy/install-cumulative-updates?view=exchserve...

I have noticed that it appeared during Exchange Server Cumulative Updates, the following web.config files are automatically copied to web.config.bak before web.config is overridden. (example is Exchange 2016)

Can someone please confirm that for me?

D:\Program Files\Microsoft\Exchange\v16\ClientAccess\ecp
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\Owa
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\PowerShell-Proxy
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\PowerShell
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\exchweb\ews
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\rest
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\Sync
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\Autodiscover
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\RpcProxy
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\ReportingWebService
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\OAB
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\mapi\nspi
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\mapi\emsmdb
D:\Program Files\Microsoft\Exchange\v16\ClientAccess\PushNotifications

[#2 · Accepted solution]

Okay, I have done a cumulative update and compared the web.config files (before and after update).

Yes, the update process will create a web.config.bak file but this seems to be the original (uncustomized) web.config created during the last Exchange server installation.

In other words, before any cumulative update, you will still have to back up any customised web.config and reinstate the changes to the new web.config file.

Hope that helps.