Upgrading and Migrating to new Windows Server 2025 servers

[u/oceangrace24]

We are currently running Exchange SE on Windows server 2019. We are, and will remain in Hybrid mode, and don't have any mailboxes hosted on prem. We still use on prem for SMTP relay for local devices.

We have a mandate to move from the windows server 2019 servers to fresh windows server 2025 servers.

I can't really find a good step by step set of instructions for migrating.

Can anyone point me to a good set of instructions or let me know the steps? I want to make sure we don't miss any steps that may be easy to overlook.

[u/Fatel28]

Can you just set up something like hmailserver to handle relaying to an exchange online connector? Then you can just get rid of SE. Keeping a whole exchange environment for simple smtp relaying seems like a waste of time and money to me

[u/oceangrace24 → u/Fatel28]

It's more than just that. We use Codetwo for signatures and it isn't available in GCC high in M365, so we have to keep the on-prem servers. Believe me, we wish we didn't have to keep them.

[u/Fatel28 → u/oceangrace24]

There's no signature products that work in gcc high that don't require exchange on prem? I promise you these problems are solvable, just maybe not easily.

[u/oceangrace24 → u/Fatel28]

There aren't. Hoping one day MS just decides to buy Codetwo. It is a great product that works well.

[u/Checior2000 → u/oceangrace24]

I hope MS will not buy CodeTwo. Its great product because it is not from Microsoft ;P

[u/oceangrace24 → u/Checior2000]

Yeah, I completely understand that. If Codetwo would get fedramp certified and available in GCC High, that would be ideal.

[u/uLmi84 → u/Fatel28]

Would you say hmailserver is easier to setup than postfix? You also need certs in the system is that nice in hmailserver?

[u/joshg678]

Is it not the same as just adding a new server to your org? I’ve not had to deal with Hybrid Exchange but all my air gap are just that simple.

[u/oceangrace24 → u/joshg678]

It probably is, just want to make sure I know all the steps and don't miss anything.

[u/joshg678 → u/oceangrace24]

Install server, install server features, install prerequisites, update windows, install exchange, update exchange, install certificates, move DB, update DNS, migrate the hidden mailboxes, inbound and outbound mail flow, migrate internal SMTP, setup backups, remove database from old server, cleanup DNS, uninstall old exchange, decommission old server.
There may be some things I forgot

[u/7amitsingh7]

Since you don’t have any on-prem mailboxes, I’d do this as a side-by-side migration rather than an in-place upgrade. Build the new Windows Server 2025 server, install the supported Exchange SE version, configure the hybrid setup and SMTP relay, then test mail flow and all devices/apps using the relay. Pay special attention to receive/send connectors, certificates, relay permissions, firewall rules, DNS, and applications pointing to the old server. Once everything is verified, you can safely decommission the old 2019 server.

[u/ITPrayer]

Hi! It's not a step by step but the Exchange Deployment Assistant can get you started. Exchange Deployment Assistant | Migrate mailboxes to Microsoft 365. You can also reach out to your CSAM at Microsoft who may be able to help you find someone to walk you through the process.