Exchange Server April 2025 Hotfix Update

Hi All,

Yesterday, Microsoft has releasesed the April Hotfix Updates for Exchange Server

• Released: April 2025 Exchange Server Hotfix Updates

Exchange 2019

In my case, i’ve downloaded the Hotfix Update für Exchange Server 2019 CU15

• Hotfix Update for Exchange Server 2019 CU15 HU1 (KB5050672)
• KB5050672

Installation

Update has been sucessfully installed

Healthchecker

Now let’s run the Healthchecker.

The First run updates the Healthchecker to the current version

.\Healthchecker.ps1

Let’s run that again and see the Results.

.\Healthchecker.ps1

Exchange 2016

• Hotfix Update for Exchange Server 2016 CU23 HU15 (KB5050674)

Note: You should run the Healthchecker afterwards

Dedicated Hybrid App

• Exchange Server Security Changes for Hybrid Deployments

• Deploy dedicated Exchange hybrid app

• ConfigureExchangeHybridApplication.ps1

You need one of these Roles to be able to run the Script:

• Application Administrator
• Global Administrator

.\ConfigureExchangeHybridApplication.ps1 -FullyConfigureExchangeHybridApplication

During the Script you will need to Authenticate

Entra App

Here is the App that was created

The Certificate is valid for 5 Years

It’s the “Microsoft Exchange Server Auth Certificate”

Get-ExchangeCertificate

Permissions: Office 365 Exchange Online > full_access_as_app

The Owner is set to the User that has executed the Script

Testing

The Property “ApplicationIdentifier” of the EvoSts* AuthServer has been set to the AppID of the Entra Application

Get-AuthServer -Identity evosts* | Select-Object IssuerIdentifier, TokenIssuingEndpoint,AuthorizationEndpoint,ApplicationIdentifier,AuthMetadataUrl,DomainName,Realm,Type,Enabled,IsDefaultAuthorizationEndpoint,id, when*

Test OAuthConnectivuty

Test-OAuthConnectivity -Service EWS -TargetUri https://outlook.office365.com/ews/exchange.asmx -Mailbox <OnPremMailbox>

Test in OWA Calendar Availability (free/busy)

Note

I first did test with the Administrator Mailbox as usual. The Mailbox exists OnPrem as you can see.

Get-Mailbox -Identity administrator@icewolf.ch
Get-MailboxStatistics -Identity administrator@icewolf.ch

But the Test-OAuthConnectivity fails

Test-OAuthConnectivity -Service EWS -TargetUri https://outlook.office365.com/ews/exchange.asmx -Mailbox administrator@icewolf.ch -Verbose | fl

and therefore Calendar Availability (free/busy) did not work in OWA either

Regards
Andres Bohren