Exchange 2019 CU14/15 & Exchange Server SE are both Schema Version 17033. You can check this with the following PS command: Get-ADObject (Get-ADRootDSE).schemaNamingContext -Property objectVersion

I did a in-place upgrade of 2 Physical MX Servers (Windows Server 2022, Exchange 2019 CU14) to Exchange Server SE. You will need to upgrade one server at a time. Here are the steps: Make sure you have backups of your MX DB's, and Server Configuration. I noticed IP addresses missing from our SMTP recieve connectors but that's the least of my worries.

1: Drain transport role from MX Server

Set-ServerComponentState -Identity "ServerName" -Component HubTransport -State Draining -Requester Maintenance

2: If you have another Exchange Server in the organization, redirect the queued message to that server

Redirect-Message -Server ServerName -Target "ServerName"

3: If the server belongs to the DAG group, run the following command; otherwise, skip to ServerWideOffline

Suspend-ClusterNode "ServerName"

4: Disable database copy auto-activation and move the active copy of the database to another DAG member

Set-MailboxServer "ServerName" -DatabaseCopyActivationDisabledAndMoveNow $true

5: Block the DatabaseCopyAutoActivationPolicy

Set-MailboxServer "ServerName" -DatabaseCopyAutoActivationPolicy Blocked

6: Put the Exchange Server into maintenance mode and bring 'offline'

Set-ServerComponentState "ServerName" -Component ServerWideOffline -State Inactive -Requester Maintenance

7: Verify MX Server is in maintennace mode

Get-ServerComponentState "ServerName” | Select Component, State

8: APPLY ANY WINDOWS UPDATES AND REBOOT PHYSICAL MX SERVER

9: Run Setup Assist PowerShell script (this ps script is installed on every instance of Exchange Server)

C:\scripts.\SetupAssist.ps1

10: Reboot MX Server again to clear any pending reboots/updates.

11: Install Cumulative Updates via Unattended Setup or GUI

I:\Setup.exe /IAcceptExchangeServerLicenseTerms_DiagnosticDataOFF /Mode:Upgrade

**note: I have upgraded Exchange Server's in the past using the CLI commands, but this upgrade failed doing so. I had to double-click the setup.exe. This installed Exchange Server SE successfully for some reason.

12: Once Complete, verify Exchange Version

Get-ExchangeServer | fl Name,Edition,AdminDisplayVersion

13: Remove Server from Maintenance Mode and Resume Roles

Set-ServerComponentState “ServerName” –Component ServerWideOffline –State Active –Requester Maintenance

Set-ServerComponentState ServerName –Component HubTransport –State Active –Requester Maintenance

Resume-ClusterNode –Name ServerName

Set-MailboxServer ServerName –DatabaseCopyAutoActivationPolicy Unrestricted

Set-MailboxServer Servername –DatabaseCopyActivationDisabledAndMoveNow $false

Set-ServerComponentState “ServerName” –Component ServerWideOffline –State Active –Requester Maintenance

Set-ServerComponentState ServerName –Component HubTransport –State Active –Requester Maintenance

14: Verify MX Server is out of maintenance mode Get-ClusterNode "ServerName"

15: Run Health Checker PS Script (another Exchange Server install provided script)

.\HealthChecker.ps1 -Server EXCH1,EXCH2,EXCH3

.\HealthChecker.ps1 -BuildHtmlServersReport

16: Now repeat for all of your other Exchange Server 2019 CU14/15 MX Servers! Good luck and cross your fingers if you have to watch the dreadful GUI progress bar.